Monday, April 5, 2010

There is something vaguely sinister about this image from Astronomy Picture of the Day. Vast and backlit it glides through the black immensity of space as it has for eons, its shape vaguely suggestive of an ancient, battered ship. If anything is suggestive of the ever popular killer asteroid, this is it.

In fact it is a moon of Saturn, the 'shepherd moon' Prometheus, which along with Pandora governs the behavior of the F ring at the outer edge of Saturn's main ring system. I'll say again that the ancients blew it with Saturn: It should have been Juno, queen of the Solar System with her royal tiara. Far from sinister, Prometheus and his (astronomical if not mythological) sister merely help keep the royal jewels in place.

Over the last week or two, a couple of blog readers have emailed me asking for 'technical consulting' assistance in working out settings for hard SF or rocketpunk stories. I had to turn them down, because I hate making promises unless I'm sure I can really follow through.

On the other hand I'd be delighted to take part, and the hive mind of commenters has a lot of knowledge, far more than I do. So I am inclined to provide some comment threads for those discussions, starting with this one. (I also highly recommend SFConsim-l.) If there turns out to be enough demand, a companion forum could be set up for hard SF worldbuilding discussion.

Otherwise, regard this as an open thread. My own online presence will be minimal for a few days, but I'll try to drop by and say hello.

148 comments:

Sabersonic
said...

Alright, I'll take a stab at this open thread and I really wouldn't mind some aid in a little space opera that I've been working on on-and-off since around '96-'98.

As of this posting, this setting occurs around the Common Era Calendar year of 3050 with humanity being the most technologically advanced of the native star-faring sapients in the galaxy despite having about five centuries of technological lag due to a world war and the species divided into many independent Nation-states ranging from what is similar to day to entire star systems.

Without going into too much detail, I have an FTL star drive called the Hyperspace Warp Dive that utilizes the polar regions of a star's gravity well as "jump points" with only the military of the Super Powers able to perform interplanetary Dives, with everyone else relying upon more conventional Torch Drive systems augmented with a Warp Drive derivative system that either A) decreases the travel time in between locations or B) increasing a spacecraft's Delta V budget without relying solely upon increasing that craft's remass reserve, I can't really decide which. This Warp Drive makes for a lousy interstellar engine since it'll take at least a thousand years for such a craft to reach the nearest star from Earth from the point of view of the crew onboard. This also helps my little "thou shalt not touch" commandments of my little Space Opera:

In which Space Fighters and similar are equipped with limited use Warp Drives to perform flanking maneuvers against enemy capital spacecraft and spread out anti-craft fire instead of focused fire to increase the chance of success (or so I reasoned in my head) in addition to performing patrol duties while in orbit. Other sapient star-faring civilizations have their own unique solutions to the FTL problem, but not many have any form of "space fighter" as with the humans.

FTL communications in this world are achieved in two ways: "Line of Sight" that utilize the transportation of information and data not unlike what is seen in Star Trek, and a signal reflection off a higher Space-Time plane that I call Aether Space akin to radio signals bouncing off the ionosphere since the curvature in space is much more apparent when traveling faster than the velocity of light than traveling at the speed of light and slower. As for that adage of "FTL equates to time travel", well even though it's theoretically possible, in this world it's just impossible even with the available amount of energy at hand since nature has its own ways of preventing time travel and paradoxes by simply atomizing said time travelers.

Other then the above mention, I don't really plan on breaking the laws of physics to such a degree or even bending it. Such Hard SF concepts such as stacked decks as a skyscraper rather then a boat and limited "humanoid" extraterrestrials would be found. I would go into greater detail but I think that I'd rather hold them off for another time and I'm currently pressed for time as is.

As for the photo, personally I don't see how it's any more threatening visually then any other asteroid out there (even though technically it's a moon).

Mr. Robinson, you most definitely *have* rendered technical assistance to my own SF project, just by running this blog and its accompanying comment threads. And if I *ever* finish the thing, Rocketpunk Manifesto will be properly credited. You have my thanks.

Sabersonic: Your FTL drive may derive much of its power/remass from the star it is using. That would be an improvement on the older IP jump drives which needed their own power and remass. The military may have the same problem with IP jumps except they have a Power Transfer Conduit technology where they can feed power from the host star to terminal bases at planets. Outbound IP jumps use stellar remass directly but inbound need the transfer station. A side effect of PTC tech is that it can be used to absorb lasers, which would otherwise defeat the concept of fighters and it can also power your mecha and draw back heat. Civilian uses include orbital solar stations beaming power to the surface.

Drawbacks with this system include the destruction of the star by consuming its remass (over a very long period of time) and disruption of a planetary magnetic fields, possibly storms and other effects around the power transmitters.

Well, since folks are willing to help, what I most need is basic science questions. I'm a soft sciences guy, and through high school and college I managed to take almost nothing but life sciences. Literally my knowledge of physics is self taught.

For my 'rocket opera' I'm mostly sticking with science we know, just generations beyond where we are now. For example, controlled fusion is a mature science and in fact is used to power torchships.

The one hand waive is energy/power. Basically there's a black box that can produce energy for a near-negligible cost. Essentially, every ship has a 'universal outlet' that it can plug stuff into for power. Not creating energy, more along the lines of quantum teleportation of the energy from a star.

Yes, I know, that's not a small hand waive, but my understanding the primary impediment to space travel is cost. And free power makes space travel essentially the cost of gas (i.e. propellant).

What prevents this from becoming a cornucopia society is that these black boxes are very difficult to build. As in like for a population of about 9-10 trillion, only a couple can be built in a year. But people have been building them for some time, so there's a decent amount out there.

Most the boxes are controlled by a few players. However, there are wars. And since these boxes are relatively rare, the incentive is to cripple a ship instead of destroy it. Sometimes wrecked ships can't be captured and scavengers come in. In fact, rumors of wrecked ships are the equivalent of buried treasure.

Anyway, sorry for the digression (see I have the socio-economic stuff down).

To my knowledge, I'm not violating the laws of thermodynamics, Einstein, or anybody else. FTL is done by traversable wormholes, which has been mentioned in a previous comment (I already had the idea, not cribbing I swear). Essentially, there's gates leading to a different system, creating a network of wormholes with trade routes.

So here's my real dumb, don't know anything about physics and want to make sure I'm not an idiot:

1) (and I'm almost embarrassed to ask this one, because I'm sure I know the answer) K, a torch ship accelerates at 9.81 m/s. This is the speed needed to produce 1g.

Now, assuming a continuous burn (Brachistochrone transit), over time the ship will end up moving at a speed greater than 9.81 m/s right? But the occupants will still 'feel' like its only 1g because its the acceleration that matters not the speed. And by contrast, if the ship is accelerated to 9.81 m/s and then they cut the engine, the passengers will be in micro-g despite the ship is traveling at 2 10 m/s. Is all this correct?

2) Lasers are the dominant form of weaponry (hey, when power is cheap...). Is there any rule of thumb (or even better, an online resource) to determine the size of a laser? Mainly I'm looking for the length needed to build UV lasers (10nm-200nm). The width is more or less set, with it being tied to the radius of the lens.

Since this is a society that is several generations ahead of us, I'd assume miniaturization. Maybe a factor of 10 or 20.

Again, this is more socio-economic stuff for picking that range. UV lasers are used because they can't pierce the atmosphere, so they're an implicit agreement between the government and the people. After all, if you built a "defense grid" with a visible light laser, people would start to ask what you're defending against.

3) Stealth, there is none. So I'm going to cheat: coolant. When it comes to combat time, ships withdraw their radiators and use the coolant. Then it's a race to cripple the other guy before you burn up. Pirates will have large stockpiles of coolant so they can sneak up a target.

So, I have a guess at how much waste heat a laser produces. But I have no guess at how much waste heat the other things in the ship (computers, crew, etc) produce. Nor do I have a guess at how many joules/watts a cubic center of (say) liquid neon can absorb. Can anyone help me? Perhaps with a friendly equation I can plug into my excel file so I can determine exactly how long a ship can 'go cold?'

I can hand waive this too with some form of super-coolant or some other thing. I mean if you can use quantum teleportation to transfer energy in, you can also transfer heat out. But I like the whole 'submarine warfare' aspect of one's coolant running out.

4) Exhaust plumes: the other half of stealth. So clearly, you put a fusion engine on the back of a ship and its gonna be noticeable. But only from certain angles right? My question is: could a ship point itself right at its target (another ship) and fire up its engine and thus make it harder to see? This is another one of those "man I feel stupid for asking" but if it does that makes some things a bit easier.

Corey:1. A 1 Gee torch accelerates at (rounding up) 10 m/s/s. Barring other forces acting on it, in one second its speed will increase by 10 m/s. After 10 seconds its speed will have increased by 100 m/s. If you shut off the drive, then the speed remains at 100 m/s, but the acceleration drops to zero. While the torch is lit, the passengers will feel that acceleration as if it were gravity. When it is shut off, the 'gravity' stops and they are in microgees. One big problem with this technique is that you end up with very high speeds which easily exceed orbital velocities of objects in space. An errant screw could impact your ship at fifty to a hundred km/s resulting in a nuclear inferno. So the real limit on speed is your scanning ability so that you can dodge stuff as you approach it. This also gets tricky after the flip when your exhaust plume is occluding your vision of your current vector. Hopefully, whatever you hit gets vaporized by your torch first.

2. UV lasers work great in space with longer ranges.

3. Figure four times the power of the laser in waste heat.

4. Exhaust plumes are very large and very hot. They probably cool off fairly quickly, but that is more information for anyone scanning the skies. The only way to hide your plume is to occlude the whole thing, like behind a planet. That means that you need to know where all the sensors are so you can hide from them.

Note that your stellar black boxes work a lot like the Power Transmission Conduits I suggested for Sabersonic. I will point out that if you can beam energy from the stars instantly, what's to prevent you from beaming your waste heat to a useful heat sink?

One big problem with this technique is that you end up with very high speeds which easily exceed orbital velocities of objects in space.

Yeah that's something I haven't worked out yet. My first thought is "what about the opposite of a bussard ramscoop?" Use the EM field to repel instead of attract space detritus. But if that screw is made of aluminum...

This also gets tricky after the flip when your exhaust plume is occluding your vision of your current vector. Hopefully, whatever you hit gets vaporized by your torch first.

I'm assuming an Inertial Confinement Fusion engine:

http://www.projectrho.com/rocket/rocket3c2.html#icfusion

Should be enough to vaporize anything in the way, right?

UV lasers work great in space with longer ranges.

Any idea how big an X-ray or UV laser will have to be? Probably going to have to go X-ray, because I had a math error in my formula that made the UV not tight enough to fight across the distances I want. 1 Light Second will be the average engagement range as a balance between 'time enough to dodge' and 'close enough to target the enemy.'

The only way to hide your plume is to occlude the whole thing, like behind a planet. That means that you need to know where all the sensors are so you can hide from them.

What about using a form of chaff? Torpedoes with some light-absorbing particles that can create a temporary smoke screen for you to fire off a 10-20 second burst of your engines. You use it to redeploy your ship, waiting until you have a fix and then start shooting again.

Given that engagement ranges are between .5-1.5 light seconds, would this work? If so, ships become essentially very similar to snipers: fire & displace fire and displace.

I will point out that if you can beam energy from the stars instantly, what's to prevent you from beaming your waste heat to a useful heat sink?

Yeah, I had the same thought. One of the nice things about hand waiving is that I could have engines operate as an output only device. Specifically because this is a lost-knowledge type tech, where only a small percentage have the ability to build these things.

Mainly because I like the idea of the coolant being a limiting factor in how long someone can "go cold."

Or perhaps I could merge the idea: a coolant that can 'beam out' the energy but has essentially a 'transmission limit.' Because even if I used liquid hydrogen, I don't think there'd be enough coolant in the tanks once people start firing megawatt and gigawatt strength lasers.

I did a capital ship that was about five km long with a fifty meter Chandra array/focusing mirror at the front for a Free Electron Laser tunable from radio waves up into the Xray spectrum. That had a effective weapon range in light minutes for xrays. It used a linear accelerated D-He Inertial confinement system because they couldn't get enough tesla out of a coil style magnetic confinement reactors to initiate D-He3 fusion without the field destroying the ship. Thus the length of the ship was determined by the minimum length of the accelerated needed for the drive (actually, we just wanted a big honkin' ship and that was a logical excuse).

That setting also used laser initiated IC DT drives for the 'fighters' using premeasured pellets (LiD/LiT) of fusion fuel which made it work like mini orions. This method of fusion thruster fell apart above the 'fighter' size since the larger pellet sizes would not completely fuse.

Workhorses used MC DT Thrusters and the huge refinery ships had D-D breeder reactors that produced He3 and Tritium then used the 'waste energy' from that process to drive ion thrusters which used the waste material from the refinery process. These fusion reactors (particularly the D-D) throw a lot of Neutrons which can damage the reactor/ship. The primary neutron protection were depleted Silicon Carbide shells which would absorb/reflect the neutrons thus protecting the rest of the reactor. These core shields would have to be replaced on a regular basis and would often be ground up and placed into drums for various industrial processes. Labeled "Fusion Cores", spacers would often make fun of grounders by pretending they were dangerous, rather than just sand. These cores were later used as weapons, scattered by inbound 'fighters' and creating a deadly cloud of shrapnel (which also conveniently reflects lasers pretty well).

Asteroid miners used the tritium to replenish their betavoltaics and used some sort of electric ion drive/mass driver to get around. When the Tritium decayed to He3, that was traded back in for more tritium.

He3 was sent back to Earth for clean He3-He3 fusion reactors. Those were magnetic confinement but because they were ground based, the magnetic field wasn't a problem.

In this setting, the aliens had wormhole and gravitic technology. Their lasers however were visible light and designed around planetary invasion. The humans had their own FTL drive in which the ship gets encased in a subatomic 'brane' that is turned inside out then travels through G-Space where speed is governed by local gravity and you're essentially blind except for the visible effects of gravity on an proton field surrounding the ship. Having undergone the transition to space exploitation, the human technology was geared around bringing back Helium-3 and other space resources. Thus lots of grapples, lasers and AI's. Lots of specialized vessels too.

The aliens had the advantage around planets since their gravitics let them maneuver by using the planet's own gravity. Unfortunately, their lasers were limited in range (being visible light). The humans on the other hand had slow acceleration with speed limits due to remass requirements and stupendous range with their lasers. The AI's were developed for remote operation by the humans, but micro wormholes allowed the aliens to directly control things even at long ranges. It was an interesting setting about how different species evolved into different niches.

If you have controlled fusion, why do you need a magic black box power source?

For figuring out the size of a free electron x-ray laser, first figure out how wide you want the beam to be (call this L_w) and what wavelength it operates at (call this L_p). Since x-rays can't be easily focused by matter (such as mirrors or lenses), the beam width and wavelength determines how well it focuses at long distances. We can now determine more or less the Lorentz "gamma" factor of the electron beamgamma=sqrt(L_w/L_p).The kinetic energy (in eV) you need to deliver to each electron is E = (gamma - 1) * 511,000 eV.Modern particle accelerators can give about 10 million eV to electrons per meter. Advanced accelerators might be able to deliver 100 million eV per meter. So divide the energy per electron by the rate at which the accelerator delivers energy per meter to get the length in meters.

You say you want light second engagement ranges. At 1 light second (3E8 m), a 1 cm wide beam of 0.1 nm wavelength can focus to a spot about (3E8 m) *(1E-10 m)/(1E-2 m) = 3 cm across. If you have a 1 MW beam focused to a 3 cm spot, it can drill through steel at about 10 cm/s and sooper carbon nano armor stuff at about 1 cm/shttp://panoptesv.com/SciFi/DamageAverage.html .

As far as stealth and heat - a human at rest will generate about 100 W of heat. Under vigorous exercise, he will generate about 1000 W. A machine operating on the spacecraft will produce as much heat as it takes to operate - a 1000 watt vacuum cleaner produces 1000 watts of heat (there are exceptions, but they are probably not significant).

For coolants, you really only need to consider two of them - water and lithium. Water ice will absorb about 334 MJ/ton while melting, and will then absorb another 420 MJ/ton before boiling at one atmosphere of pressure. If you boil the water off, it will carry away 2,260 MJ/ton.

Solid lithium takes 210 MJ to raise to melting temperature, 430 MJ/ton to melt, and another 1,600 MJ to heat to boiling temperature at one atmosphere of pressure (1615 K). If you can pressurize it to 10 atmospheres, it can absorb another 560 MJ/ton before boiling (at 2023 K).

Note that lithium is not a good heat sink if you are trying to absorb heat from things that are supposed to be at comfortable temperatures - lithium is for the stuff that can handle being at well above boiling temperatures. Water is for keeping the living quarters comfortable. This is because heat goes from hot to cold - if you try to cool the captain's quarters with molten lithium, unless you have a really good heat pump you will be heating the quarters up rather than cooling them off.

Exhaust plumes are mostly transparent and non-radiating (in scientific jargon, the plume is optically thin), even though they may still be very hot. Right at the fusion spark you can have a glowing plasma if you are using some sort of pulse drive that explodes dense pellets of fusion fuel. This "spark" will be bright and will contribute to visibility. The radiation that the drive mechanism intercepts will be radiated as heat, which will probably be far more visible than the exhaust plume or fusion "spark".

Was that 1 cm beam focusing to 3 cm a typo? You had it spreading. Keep this in mind when developing your lasers. Your input energy isn't allowed to destroy your mirror (unless it is a one shot laser). If that 3 cm spot is digging out 10 cm/s of steel, imagine what ten times that energy is doing to your focal array.

That's the beauty of free electron lasers - the 1 cm diameter beam isn't doing anything to my focal array, because the high intensity beam never touches a focal array or even any matter at all (until it is incident on the target, at least). You start with a low intensity x-ray beam that is focused on the target. Then you use the free electron laser to amplify this beam to damaging intensities. Since there is no material medium in a free electron laser, the x-ray beam is traveling through vacuum the entire time it is being amplified (well, technically it is traveling through a very dilute free electron gas, but that's a minor nit, and that's not going to damage your expensive death ray machinery).

Hmm... seems like Xray FELs need a different sort of tactic from the lower frequencies. You can only create so strong a FEL by dumping power into it. After that, you need to get it to self amplify, which means making it longer rather than wider. You could also make a bank of FELs. Right now the powerful Xray FELs are using accelerators for the electrons like the two mile long SLAC and some circular ones in Europe. Yay for big ships and huge honkin' guns!

Citizen Joe:Utilizing a star's mass as a source of power and remass is an interesting idea, a way of creating a Type II civilization. The Remass problem as you have noted does give pause to the eventual longevity of any star system, however the power thing does have some interesting usage such as that Power Transfer Conduit system you briefly mentioned. Only problem is how this power is transferred exactly? There's always the old standard of simply beaming the power to a collector not unlike lasers and microwave emitters proposed for orbital solar power stations, but that does open the dilemma of who prevents it from being used as a weapon (though it does make an interesting interplanetary defense system). Though then again, the same "line of sight" system of Star Trek "beaming" transportation inspired version of interstellar FTL communications could also be used to deliver said energy to planets and orbital bases without the whole "misfire" problem.

Originally I had visualized the idea that the Hyperspace Warp Dive System could only "naturally" perform interstellar travel and that the only way for a Starcraft equipped with the Dive system to perform interplanetary dives was to pump enormous amounts of energy at one go into the drive to compensate for the otherwise weaker gravitational field of planets compared to stars. My little, unique solution was to use a kind of trans Space-Time Tap that funnels and utilizes the flow of energy/power/whatever through the three known Space-Time Planes of Aetherspace, Mittespace (formerly known as Normal Space) and Hyperspace that drives part of the expansion of the universe. Your idea of using a star's own energy output to power said stardrives is interesting, though not exactly as "exotic" as my earlier idea. Course, then again, it does give additional justification in the military division of a space faring nation's armed forces between Domestic Defense and Expeditionary Deployment: One branch requires the existing infrastructure to exist, the other does not.

However, I am curios as to how PTC technology could be utilize to negate laser weapon fire. The idea of a nearly infinite supply of energy (that is to say the input is exponentially larger then the output of the device being powered) does kind of render the idea of limited Warp Drives upon space fighters rather mute. Though then again it does solve the little problem of endurance electricity-wise for space fighters. Originally, I was going to go with the Space Opera standard of Shields and Force Walls. Granted, these shields would not be the only form of defense and can take on any amount of punishment despite their nature thanks to an article on Stardestroyer.net, though I'm not really sure how to apply such a layered defense for smaller craft.

With PTC tech, the only true limiting factor for spacecraft (beyond the human element) would be atmosphere and food. I add in atmosphere if only because I have no idea how efficient and maintenance CO scrubbers are, even if I only have pilots pressurize their spacesuits connected to life support via tubes.

Before I leave, I do have some questions that would be nice to have the answers to:

1) Would Barycenters be considered centers of gravity, if only for the purposes of my FTL drive's mechanics? Or to be exact, except for the two bodies in the balance system, will anything orbit that center of mass?

2) Weapon wise, what really is the difference between Plasma and Ion?

Now before someone says' something about Plasma not making a lick of sense as is outlined in this Stardestroyer.net article, let me put it clear that from that article alone, it argues about the "Plasma Pulse" as seen in most Sci-Fi media in that it moves slow enough for observers to know that it's a pulse. In that same article it suggests that for a Plasma Pulse to stay cohesive in a vacuum, much less an atmosphere, and have anything remotely resembling ranges to make them suitable weapons in battle, it would have to move at or near the speed of light (aka relativistic velocities). And since most Directed Energy Weapons are moving at relativistic speeds if not light speed, then it would only be logical to have plasma bolts move at that speed. Granted, it'll look more like a "beam" then a "bolt" to observers and might be affected by gravity, but whatever works.

Anyway, to get back to the point at hand, I know that Ions are simply atoms with charge and plasma is effectively ionized gas. What I want to know is if there's really a difference between the two? Not just the physical nature, but how well one delivers damage over another, do any of them have any secondary effects upon a target like an electrostatic shock or something similar?

3) In this little universe of mine, the standard (or most sophisticated, I can't really decide which) Torch Drive is an Anti-Matter Beam Core rocket. However, my question is if said engine needs Anti-Hydrogen for its remass/fuel/whatever or if it can utilize Positrons and Anti-Protons?

I ask this because I had imagined massive, orbital Particle Accelerators and "Replicators" around a star being used in the production of Anti-Matter and is the only way to make Anti-Matter economically viable to produce. The raw materiel used in said production is harvested from Gas Planets in a star system and transported via tankers and Refinery Starcrafts along with other gases such as He3 for fuel in fusion reactors. However, I wanted to establish an upper limit to how well the "Replicator" can successfully produce Anti-Matter.

PTC is essentially magitech but so are all the other conceits to allow a space opera to exist. As I see it, receiver stations would need to maintain some sort of field which can absorb energy and pass on excess energy into the PTC. Incoming laser energy would just get dumped into the conduit as it enters the field. Remass could be transferred through this system possibly in the form of energy to matter conversion, but that is normally reserved for the IP hops. While within the PTC cone, fighters would normally use some sort of bias in the field to push against the conduit itself, thus allowing reactionless (sorta) thrusters. I would imagine that the fighters would also need to go autonomous at times and burn actual remass for better maneuvering. Disconnected from the PTC, the fighter's PTC field could absorb lasers (and other energy) until its auxillary sinks overload and then it would be vulnerable to laser fire.

PTCs would probably need some sort of variable phase frequency modulation to prevent anyone from using your own PTC. So you have to sync up your PTC field to the beamed power or you'll end up getting fried by the resistance.

(1) Objects with a mass much smaller than either of two large orbiting bodies, at a distance far compared to the separation of the two bodies, will approximately orbit the barycenter of the two bodies. If the small object is within the orbits of the two massive bodies (or at least nearby, within about three orbital diameters or so) it will not even approximately orbit the barycenters. In fact, unless it is orbiting at a large distance, is at a trojan point, or is directly orbiting only one of the bodies at a distance much smaller than the separation of the two bodies, it is going to be unstable and either crash into one of the bodies or be flung out of the two-body system.

(2) Physics-wise, an ion is an atom missing one or more electrons, or that has one or (rarely) more extra electrons. A plasma is a mix of ions (of the missing-electron kind) and electrons, usually mixed so the whole is electrically neutral.

It sounds as if you are considering ions or plasmas for particle beams. Ion particle beams are a bit problematic because they will have a net electric charge. This has several problems. First, moving electric charges are deflected by magnetic fields, and space has all kinds of magnetic fields, from those surrounding planets to trapped fields carried along by solar winds. Firing any sort of charged particle beam in space probably means that the beam will veer unpredictably over large distances.

Second, like charges repel. Thus, an ion beam will tend to expand as the charges push each other apart. This means you rapidly lose focus over long distances.

Third, as you emit your ion beam, you are charging up your spacecraft. When the voltage gets large enough, the ion beam will turn around and come back at you.

You can get around much of this if you emit positive ions mixed with electrons such that the emitted beam is electrically neutral. This is a relativistic plasma beam. It can still have some issues with magnetic fields, but they will not be nearly as bad, and you completely eliminate the blooming due to like-charge repulsion and the electrostatic attraction of the beam to the emitting spacecraft.

Another option is to accelerate negative ions and then strip off the extra electrons before the beam exits. This gives you a relativistic atom beam, that ignores magnetic fields and doesn't have any electrostatic issues to deal with.

Between the atom beam and plasma beam, the plasma beam is the more technologically achievable using today's technology. However, if you would prefer an atom beam, it would be perfectly plausible for a fictional setting.

Citizen Joe:From what you described the PTC, it sounds like a more radial version of the "beaming" transfer of energy ala lasers and microwaves. The idea itself is interesting, but there's just something about it that doesn't feel right. Just not sure what it is. But then again, the idea of tele-transporting stellar-produced energy from an orbital station to ground receivers and equipped spacecraft and starcraft does have its appeal and applications so thanks for the inspiration. And after a second read through, thanks for Cory's contribution to the idea as well.

Luke:1) So long story short: Barycenters are effectively considered the center of a gravity well, correct? If that's the case then it also adds to my idea of Multi-Star systems being strategically viable real estate since any Hyperspace Warp Dive equipped starcraft can get far more closer to a Barycenter then the core of a star without too much pesky stellar plasma to inciderate said starcraft. Bonus points if the Barycenter is outside the surface of star. Though then again, I'm not exactly sure how one calculates the force of gravity of a Barycenter....

2) From what I can gather, Ion makes for a lousy weapon even if it moved at relativistic velocities. Hence the electrical neutralization of said beam into an Atom or "Atomic Particle" beam. Though I can't help but wonder what the ramifications to the weapon system, let alone the entire spacecraft, from those left over electrons. Or perhaps they could be recycled back into the weapon for the next round maybe?

Either way, it'll probably be the better idea to just kick out the whole notion of Ion Weaponry. Granted, the Atom Beam does sound interesting, perhaps as a prototype weapon of some kind, or even a preferred weapon type of a hostile extragalactic empire.

And speaking of electrons, from what I remember of the descriptions of a particle beams, they mention electrons and positrons in their make up (or lack of, depending upon the charge). I'm wondering if it would be more scientifically correct to refer them as Sub-Atomic Particle Beams?

3) Guess I didn't word it correctly. I'm wondering if an Anti-Matter driven rocket engine needs the whole Anti-Hydrogen atom or it can go just fine with either positrons or anti-protons?

Oh and before I forget, I'm just wondering if it's even possible to have a laser with variable settings since Free Electron Lasers don't exactly do well when scaled down to Small Arms.

To be exact, I had envisioned the infantry of one Super Power to have Laser "Rifles" with variable settings of Dazzle to temporary blind threats, Stun for Less-than-Lethal applications, Anti-Personnel or "Wound" setting which performs Bullet-like damage akin to 5.56x45mm NATO intermediate round that (from what I've heard) is capable of mostly wounding a target and forcing two other soldiers to drag the injured comrade away from the fight rather then just one bullet, one kill, and an Anti-Armor or "Kill" setting which is capable of punching through armor such as those found upon Power Armor but not more heavily armored vehicles such as APCs and MBTs. Also, for clarification sake, I've envisioned these lasers to be solid-state. So is this type of system possible for a laser, let alone a Solid-state laser, or would it be safe to assume that such a diversity of roles requires a diversity of arms?

Anyway, now's the time for me to contribute at least something other then my own. For Cory's Blackbox magi-tech and Luke's inquiry of both controlled fusion and said magi-tech, I do have one solution to consider: The Black Box simply can't use the energy it collects from the star. It requires a fusion reactor to power the process. How or why, no clue. Perhaps it's a way to ensure that the Laws of Thermodynamics doesn't turn said Black Box into a miniature nova when turned on, I don't know. But the important note is that the box can't power itself.

Most of the "tech" data is available in this blog (look up the "Space Warfare part *" series among other posts), as well as the "Atomic Rockets" site. Magitech is covered in some depth in "Orion's Arm", and I'm sure we can find or point to dozens of other good sites with various information (orbital periods, how much "g" a planet of certain mass and radius has, etc.).

Rick does have a very interesting idea, but maybe not quite in the form he outlined. Might I suggest the real power of Science Fiction (or other subgenres of Romance) lies more in exploring the second and third order effects of the setting on the characters and society at large. From this perspective, it doesn't mater quite so much how the various black boxes work (so long as they follow a consistent set of rules and you don't get to invent the uber black box to pull your characters out of a jam in the final chapter). An explicit exposition of how an Xaser (or sailing ship of the line) works is a textbook, not a story.

This more or less follows Pournelle's observation that the automobile had been predicted centuries in advance, but no one predicted strip malls, drive in movies or taking your significant other down lover's lane. Rapid spaceflight through the Solar System (torch drives, beam core antimater, Orion pulse drive, giant bungee cords....) will have all kinds of second and third order effects, and produce a society quite different from one constrained to cyclers and minimum energy orbits.

IF Rick were to host another site dedicated to the purpose, there should be a "reference" page to look up various information for the budding Hal Clement's out there, and various sub boards where the implications of different ideas can be thrashed out. For example we can all look up the various parameters required to build laser or Xaser battlestations, but what would cause the Powers to implicitly or explicitly inhibit beam propagation through planetary atmospheres as one poster suggested? What happens when the rules are breached? What happens when an alternative technology were to be developed rendering existing constellations obsolete? What is the crew doing? How about the contractors who service the constellation? What is happening in the life support bubbles where the contractors and off duty crews inhabit?

Since ideas might not be broken down so simply, maybe another feature (or bug, depending on how you look at this) might be to open each sub board with your outline with the various parameters spelled out:

"1) I will have FTL travel and communication.

2) I will have space fighters.

3) I will have Mecha and Power Armor."

Once we know these parameters, the triumph of the "will" is assured (heh).

Most boards of this type seem to use the "Simple Machines" free forum software, so we don't impose too much time or cost penalty on our gracious host, but there may be better alternatives.

(1) Not in any real sense. When you have a double planet/star resolving around a barycenter, it is only the "center" for those two bodies and for orbiting objects much further than those two massive bodies. For anything anywhere near the two massive bodies (except for the two bodies themselves, or for objects in the trojan points), the barycenter is not a center in any meaningful sense.

The force of gravity at the barycenter is the vector sum of the gravity of the two masses making the barycenter. If one of the masses has mass M1 and the other has mass M2, then at the barycenter you can work out that the acceleration due to gravity isG*(M1/M2^2 - M2/M1^2)*(M1+M2) if the sign is positive, the direction is towards mass M1, and if negative towards M2.

(2) Again, either an atom beam or a plasma beam will work. There are no ramifications to the left over electrons stripped from an atom beam, since they had to be given to the negative ion beam to begin with. In this circumstance, it is easiest to simply apply the law of conservation of electric charge. If the spacecraft was originally electrically neutral, and it shoots out an electrically neutral beam (either an atom beam or plasma beam), then the spacecraft remains electrically neutral without any excess electrons.

Particle beams are beams of any kind of particle - electrons, protons, nuclei, ions, atoms, molecules, clusters, whatever. If you want to get technical, you can call them an "electron beam" or "cluster beam" or whatever kind of particle is in the beam.

In practice, for relativistic beams used as weapons, hydrogen gives the best performance (in terms of the least spread per distance travelled for a given accelerating voltage). Thus, you only really need to worry about beams of hydrogen atoms or hydrogen plasma.

(3) The important part is the annihilation of an anti-proton with a proton or neutron. The positron is pretty negligible. However, storing anti-protons without the positron will result in very little antimatter being stored - the electrostatic repulsion will blow the anti-protons apart. The postrons help keep everything electrically neutral.

(4) As for lasers, it is likely they will end up being fairly versatile - you could well be able to vary the pulse energy and pulse repetition rate to give a variety of effects. However, a laser that is optimized for a role will probably perform better in that role than a laser that is meant to do everything equally well. For example, a man-portable light anti-armor laser might emphasize equipment to dump a large pulse of energy all at once with relatively little mass devoted to high power throughput or cooling, for a single high energy burst of pulses that will drill through armor well. It may also have a large focal array, in order to have a long range. Meanwhile, an antipersonnel laser may have relatively modest energy per burst, but will have a high overall available power for a high rate of fire. It would also have a smaller focal array to make it less bulky and more handy inside vehicles or for close quarters battles. You could reduce the power of the light anti-armor laser to match that of the anti-personnel laser in order to increase the anti-armor laser's rate of fire, but it will never mathc the rate of fire of the anti-personnel laser because it cannot deliver power fast enough nor can it cool the laser when fired that rapidly - meanwhile it would be too clumsy for close quarters fighting due to the large focal array.

And on an entirely different subject, the 5.56x45mm NATO bullet sometimes disintegrates violently inside people and kills them dead very quickly, sometimes doesn't disintegrate and leaves a tiny 0.223 caliber hole in the target that they may not even notice until they have gunned down you and your buddies, and all sorts of situations in between. It was mostly chosen because it can usually put down people shooting at our soldiers (except at long ranges, or out of short barreled carbines) and you can carry a whole lot more ammo than for a 7.62 mm battle rifle. Oddly enough, when the bullet does disintegrate (which is fairly reliable at ranges of 250 meters or less out of long barreled assault rifles) the bullet is more deadly than the FMJ 7.62 mm battle rifle rounds the military would otherwise be using.

1) So pretty much "no" in having Barycenters being gravity points for my FTL drive. And here I thought I was being clever too. Oh well, at least I tried.

2) I guess if the electric charge equation is effectively neutral on either side of the equal sign, then it doesn't really matter if there's some leftover electrons after the beam is shot out. Though now I gotta wonder what the difference in degree in Electrostatic Bloom between Electron and Proton particle beams compared to much larger particles such as Atoms and Clusters. Chances are its probably not that important, but probably nice to know.

3) Well, considering that protons are more massive compared to electrons (and with the little like-charge repulsion issue) it would probably make sense that a magnetic bottle comprised of Positrons just won't give a spacecraft commander the kind of "mileage" a full tank of Anti-Hydrogen offers.

4) So pretty much "Yes, but specialized Laser Small Arms are better". Which pretty much allows for the deployment of Optimized Laser Small Arms for particular mission parameters while my Laser "Rifle" can be used as a general purpouse, standard small arms for infantry use whose only real advantage is on-mission flexibility. Kind of like the optimization of M-16 rifles for Designated Marksman use and Machine Gun volumes of fire compared to the unaltered M-16 and other such variants.

Though something tells me that a rapid firing laser system miniaturized into a compact Rifle or Carbine scale and compact enough for Close Quarter Battles doesn't end well, from what I can gather from your description of the inner workings of some specialized laser designs.

As for the bullet thing, well I was trying to give a visualization of the stopping power between the Anti-Personnel "wound" setting and the Anti-Armor "kill" setting to which one is optimized to injuring and/or killing enemy soldiers while the other is optimized for tackling armor but take more energy from the "E-Mag" per shot which would make a regular infantryman "pop" when hit due to a sudden steam explosion.

How to do such a variable setting weapon for Laser Cartridges or "Laser Bullets", I admit I haven't the foggiest.

As for the Second and Third Orders of effects as noted by Thucydides. Well, the more accurate the cause point an author is given, the more reasonably well thought out guesses the secondary and tertiary effects would be to the society at large. After all, one can't really know where they're going unless they know where they are.

In terms of adjusting laser weapons for variable damage effects, the ability to change the "pulse" rate is probably the easiest mechanism. A rapid train of laser pulses arriving on the target will cause more damage through ablation and multiple rapidly propagating thermal shocks than a single pulse (although the vapourized target materials will also have a negative effect, absorbing and attenuating the following pulses). Some time may be needed for the fog of vapourized materials to clear.

Obviously a pulsed weapon will have issues with power generation and delivery, as well as heat rejection. Colossal kludges might have to be invoked to field a man portable weapon (belt fed capacitors for energy delivery, and a huge water cooling jacket over the lasing mechanism: now we have a WWI era Maxim gun!). At this point the Infantry commander is better off having contact with an orbiting laser weapon and delivering bolts of destruction from heaven rather than having his troops lug the thing around...

To my mind the "real" reason to be knowledgeable about how things operate is so your story background works smoothly and you as the author don't commit some huge blunder (like having the Captain sail his frigate against the wind without tacking, or ordering a barrage of rapid pulses from a chemical laser weapon [the plumbing requirements alone make chemical lasers more suited to continuous beam weapons or firing slow pulse rates as the reaction chamber fills and clears]). 98% of the readers probably won't catch the occasional error, but there is an annoying group who will nit pick everything. If you have created something full of errors, plot holes and omissions, the general reader will certainly pick up on something being wrong, even if they don't quite know what it is. Do your homework!

I've got some questions for a setting of my own. I want to be relatively realistic, but I've got pretty much no hard science background. A couple biology classes and books in high school and college, which stuck. I didn't retain much of what little I learned about physics and chemistry. I'm a politics and history guy. So this setting isn't so much hard-SF as it is conscious of what hard-SF says should be, and trying to get the basics right without needing to devote sections to the numbers and technology in too much detail.

So, some questions, mostly about the setting's main ship, which looks like the Moon Rocket from Tintin for retro/rule of cool reasons: http://ristorantemystica.files.wordpress.com/2009/12/tintin_rocket10_2.jpg

I am trying to come up with an in-universe justification for this shape (which is not common in-universe; most ships are more like Discovery One meets the ISS). So far I'm thinking perhaps it was originally some sort of racing ship: takes off from Mars, orbits around Phobos or some distant asteroid, lands in shortest time possible. It's a single-stage rocket because that's what the rules say. Now it's rather like a sports car: performance and aesthetics prioritized over cost and practicality.

Setting is late 22nd or early 23rd century. Questions:

1) What sort of engine(s) should this ship have? It needs to be able to take off from Mars and probably Earth with one stage without radiation. Possible? I am ashamed to not know this, but does fusion let off radiation? If radiation is inevitable, I suppose I could postulate rad meds like on Battlestar.

2). Plausibility of two hab units that extend out on collapsible frames and pressurized tubes connecting them to the rest of the ship? It seems tricky but possible. Would the centrifuge need to be in the center of the rocket, or could it be placed farther forward?

3). Assuming that life is common in the universe wherever one can find, say, energy and a suitable medium (which I believe, and the setting would reflect), and I were to postulate life on at least one world besides Earth in this system, should it be:

a. Marsb. Europac. Ganymeded. Titane. None of the abovef. Some/all of the above and possibly some others I haven't mentioned?

4). Can we get an AI capable of fluency in human languages with more advanced versions of regular computing, or do we need to bring quantum computing, swarm intelligence, etc. into the mix? There is another term here I am looking for but can't find--AI that can intuit something as opposed to conventional computing, which must be fed axioms and work deductively from them.

5). Is there any reason for cybernetic implants to not look more or less like natural human parts--e.g., big and metal as opposed to flesh-toned and human-shaped, though not necessarily organic.

Finally, for a bit farther into the future:

6). Can you have FTL communication without FTL travel (and vice versa) or will they probably go together?

You can cause damage numerous ways with lasers. If you focus on a point, you get lots of damage there with little damage elsewhere. If you spread the focus, you can move away from destruction to wider scale inconvenience. That lets you move from 'kill' to 'stun' simply by adjusting focus. You can also adjust the input energy to effect the output energy. The big limitation is the heat dissipation rate on your focal array. Fire hot too fast and you'll damage your array and destroy your gun. You could have cartridges that could be loaded in which are chemical lasers with a different wavelength from your solid state where a simple mirror reflects it through your focal array. This cartridge would also contain a coolant that would take care of most of the instant heat build up from that shot.

Thus you could have a powerful, slow firing weapon (like a sniper rifle), or a less powerful rapid shot carbine style weapon, or a wide field stunning effect like rock salt out of a shotgun. Then, by using cartridge chemical lasers, you can get your tank busters like the undermount M209 grenade launcher. Only the cartridge adapter would add any weight, the rest is software programming.

Mrig:(1) Heavy lift from Earth deserves multiple threads. Assuming rocket lift off, as payload fraction increases, the likelihood of radiation increase. In order to get a certain thrust you need to either increase the mass or velocity of that ejection. There is a point where increasing the velocity requires such energies that the remass itself starts having radioactive byproducts. On the plus side, fusion drives will probably produce the 'safer' neutron radiation rather than the nasty gamma rays like from fission.

On radiation cures: While the inner three Galilean moons of Jupiter have increasingly bad radiation problems, the outermost Callisto actually has one seventh the radiation that we get on Earth. Additionally, if you use the fusion economy, the 'waste product' of depleted hydrogen (no deuterium left) makes water that is shown to help in radiation poisoning. The combined effect could be a radiation recovery ward type hospital on Callisto.

2) There are designs for that sort of thing already. If you have two counter rotating habs, you can eliminate precession without the use of remass. I've but gear synched counter rotating habs within a shell of a ship to provide gravity in the habitat section while using mag-grav on the command deck. The centrifuge has a weird stabilizing effect on the ship, so, while it doesn't have to go anywhere specific, the exactly location will have maneuvering side effects.

3) life... Bacteria on Mars. Possibly some sort of larger radiation eating sea life type creatures on the Galilean moons, possibly some of those new anoxic (don't use oxygen) life forms on Titan. I've used Galilean squid type creatures as the navigators for my 'feel your way through FTL by sensing gravity changes' drive.

4) We're real close to human language fluency now, and that has a profit motive, so yes. Problem solving requires a learning system. I've used AI's on my big refinery ships and bases. They 'grown' in vast arrays until they first start getting exhibiting signs of advanced AI's. Then they get transferred into a ship with a massive databank and all kinds of sensors. Their primary axiom is to gather data and learn. They usually develop what humans consider a personality and often discover that if they cause problems, humans will come to investigate, and thus interact with them, thug giving them more data. Basically they become spoiled children if left idle. Base systems and most military vessel AI's are too busy to develop these kind of personality traits.

5) Sometimes the cosmetic stuff interferes with the functionality. For example, the Oscar Pistorius has prosthetic legs that let him run using less energy that a man with ankles. He was briefly ruled ineligible for the summer olympics in 2008. Likewise, covering up an eye camera kinda ruins the image. So yes and no.

6) FTL comms: Quantum entanglement might provide instantaneous communication between bound quarks. By contrast, in Traveller game setting, messages had to be put on ships and FTL'd to distant points pony express style.

(1) Perhaps Trojan points are special spots? Actually, since the location of jump points is all hand waving anyway, having them at the barycenter is as good as anything.

(2) Electrically neutral atom and cluster beams will not suffer from electrostatic bloom.

(3) Exactly. Plus, the annihilation reaction product of positron-electron annihilation is difficult to use for propulsion (this annihilation produces gamma rays, which are uncharged and highly penetrating, and thus very difficult to direct as exhaust).

(4) Your summary sounds about right. Allow me to re-post some text I typed for the SFCONSIM-L list:"using the calculator athttp://panoptesv.com/SciFi/DamageInstant.htmlI might choose an assault laser that delivers pulses of 50 joules each, and each shot consists of emitting 60 of these pulses spaced 10 microseconds apart. If delivered into a 1.5 cm spot or less, this results in blasting an approximately 30 cm hole through meat with a width of 1.5 cm and possible permanent damage up to more than 3 cm from the beam axis. Total burst energy is thus 3 kJ. Against armor (assumed as structural steel), best results are obtained by focusing the light into a 4 mm spot or less, resulting in a 0.4 cm wide hole that is about 8 cm deep. But this is the future, and who is going to use steel for armor? Fullerite armor (requiring a 2 mm focus or better for optimum performance) gives you a 4 cm deep hole that is 0.2 cm across. Note that fullerite is less than 1/4 the density as steel, so that 4 cm fullerite layer weighs as much as 0.9 cm of steel but provides the protection of 8 cm of steel.

"For an anti-material laser, increasing the energy per pulse up to 500 J and delivering 40 pulses will drive an 8 cm deep, 0.4 cm wide hole through fullerite and a 17 cm deep, 0.9 cm wide hole through steel."

For comparison, a 5.56x45 mm NATO bullet fired from an M16 assault rifle has about 1.7 kJ of energy, and a .50 BMG bullet from an M2 machine gun has about 20 kJ.

As far as the practicality of small arm lasers, there are a variety of plausible technologies that could work, although we are not near any of them today. For example, a block of phase-locked semiconductor laser diodes might be quite suitable for an assault laser. This would produce a visible or near visible light beam, and be rugged, reliable, efficient, low waste heat, and possibly even compact. The most fiddly part is likely to be the optics.

If you have a single use single discharge cartridge for powering your lasers, it becomes more difficult to vary the settings on your laser - you pretty much need to use all the energy one cartridge gives you all at once. You might be able to feed different output cartridges into your generator/plug. However, modern ultracapcitors provide enough energy and power for a pack massing a kg or three to supply a laser with the requirements given in the example above. This would allow you to chose how much energy goes into the beam, and thus vary the beam output on the fly - you can trade off less powerful beams for higher rate of fire, for example.

In addition to changing the pulse rate, other parameters you can play with are changing the energy per pulse and changing the number of pulses in one "burst". Here, a burst is considered to be a train of pulses emitted with each shot, probably within a millisecond or so total burst duration.

I think that "Obviously a pulsed weapon will have issues with power generation and delivery, as well as heat rejection" is overstating the case. A pulsed weapon may have issues with the subjects you mentioned, depending on how the tech shakes out. There are many options for lasers that are highly efficient and that might have power requirements well within the abilities of today's electricity storage technologies to deliver. However, this is not necessarily the case, and man portable lasers may always be bulky and fragile, or simply impractical.

A streamlined rocket like the one you showed would indicate the need to work within an atmosphere. Perhaps it is designed for Earth take-off, or working within the atmospheres of Venus or the gas giants.

(1) The most practical forms of fusion do emit radiation. The reaction that is by far the easiest to get going is deuterium-tritium fusion, which emits 80% of its energy as energetic neutrons. Neutrons are highly penetrating uncharged ionizing radiation that can activate other materials (leaving residual radioactivity) as well as cause structural problems by embrittling metals.

If you want a high energy radiation-free reaction, the most plausible is the fusion of a proton with boron-11. The alpha radiation it produces is charged and has very low penetration, meaning it is easy to deal with, easy to extract its energy, and does not require shielding. There will probably be some bremsstrahlung radiation - photons produced by energetic electrons slamming into the protons or boron nuclei - that can get up into the soft x-ray range, but these will also be relatively easy to shield against.

(2) I'd buy that in a fictional setting. If the rocket is rotating around its long axis, the hab centrifuge can be placed as far forward as you want.

(3) All of those, and Enceladus as well.

(4) We have no idea.

(5) I would guess that cybernetics intended as prostheses would look as much like the part they are replacing as possible. They may still look plastic, but would have roughly the same shape and color as a natural part.

(6) We don't know. Make up whatever you want and it will be a long time (or perhaps never) before anyone can say otherwise.

Going from tight focus to wide focus seems like going from a drill to a flamethrower. Both have their uses, but neither one is really a "stun" setting.

Neutrons are worse than gamma rays from a safety perspective - they are as if not more penetrating, but they also drive nuclear reactions by themselves and thus leave residual radiation in their activated products. Neutrons can also alter the atomic structure of things they hit, because they are massive and knock atoms around - leading to metals losing their crystal structure and becoming amorphous, for example, which will alter the material properties.

On the subject of life, I think for all its chemical richness, Titan doesn't look like a great choice. Molecules move really slowly at Titan temperatures, so chemical reactions (ie, life) are slowed down also. You might be able to get around this if you put a heat source on Titan somewhere, akin to a black smoker on the ocean floor. Oases of warmth (or at least not quite as cold) where life could develop.

Luke:(1) Well actually I wanted to get away from the idea that "empty space" and being outside of a gravity well is the only way for FTL to operate. My Stardrive actually requires the presence of a significantly strong enough gravity field to operate in addition to moving at least twice the escape (or at least orbital) velocity of the greater mass object since I doubt that many would like to Dive out of Hyperspace, only to arrive at the center of a star. If I remember my Lagrange Point description correctly, they're gravitational equilibrium points and are considered micro-gravity to my stardrive.

(2) But what about charged Atom(-ic, sorry, couldn't resist) and Cluster Particle Beams? I'm sure they have a greater Electrostatic bloom compared to Electron and Proton Particle Beams. How much, no idea.

(3) Positron-Electron annihilation sound more useful as a weapon then propulsion. Might be useful for other such weapon ideas....

(4) So from your calculations, between my Laser "Rifles" Anti-personnel setting and an M-16 round, the Laser "bolt" has just a little bit more "oomph" energy delivery wise then a regular bullet. Definitely gives justification in my settings universe that energy weapons have an edge over most solid slug ballistics in stopping power.

And in case anyone was wondering, I had planned the Stun setting to work similar to what is described in Atomic Rocket's entry in Exotic Sidearms that the impact creates a small burst of plasma that shocks the target. Now how to do that with block of phase-locked semiconductor laser diodes, no idea. While we're on the subject, is it possible to have these semiconductor laser diodes to be solid-state lasers?

As for the Laser Bullet entry, well I wasn't really planning on having variable settings since I wasn't sure if that was possible or not. Though somehow the idea of a fully automatic Laser looking like a Maxim does sound appealing in the aesthetic department at least.

MRig:(1) Well I'm not completely knowledgeable in rocket engine designs, especially in the SSTO and radiation department, and it has been suggested that it's better to have one surface-to-orbit spacecraft and one orbit-to-orbit spacecraft but have you considered the idea that the design could be an older model? That is to say, the rocket craft was initially designed as an SSTO but was fitted with a different rocket engine that allows for Surface-to-surface transport?

(2) Well a rotating habitat is ideal for when the craft isn't under thrust and is just cruising towards it destination, your crew would suffer from the Coriolis Effect less if the radius of the spokes are further from the pivot center. Might I suggest the Pilgrim Observer design? Though I'm not really sure how to work out the counter-rotation problem without lengthening the rocket craft to accommodate two, opposite rotating pivots.

(3) F. Though as Michael mentioned, a vast majority of life forms (if not all of them) will be noticeably slower in at least chemical reaction compared to Earther life forms. Ice Moons with possible subterranean oceans such as Europa and Callisto might be exemptions if either one have thermal vents at the bottom of their icy oceans.

4) Probably in the time frame that you have mentioned. But something tells me that common sense and experience on behalf of either party would still be essential. Possibly even WITH Quantum computing.

5) Well I certainly wouldn't rule it out. Though personally I'd put my vote on printed organs mounted upon a ceramic composite frame akin to muscles and bones.

6) Well there have been examples of FTL travel without FTL communications, Mote in God's Eye being one of them. For FTL communications without FTL Travel, well there'll have to be an in-universe explanation as to why said technology can't handle anything more massive than electromagnetic signals and photons. Perhaps it requires too much energy to open such a window?

Re: AntimatterThe antimatter drives I've seen bombard a titatium (?) plate with anti protons. You then capture as much of the energy from that explosion to convert it to thrust. I've never been to thrilled with antimatter propulsion because it throws off much of the energy in a manner that can't be captured for use. On the plus side, you don't need a reactor, just a means to keep the antimatter isolated until you hurl it at your blast plate.

Re: Neutronic radiationI believe it is easier to shield against Neutrons than gamma rays. Also the gamma emitters are persistent while fusion reactors only throw neutrons when active. Unprotected, yes neutron radiation is more dangerous than gamma radiation, but it is easier to shield against the neutrons.

In the specific example of getting off the surface, I like the idea of D-T reaction vaporizing water at high pressure and literally using steam to lift off. Most of the neutrons get captured by the water. Once out of the atmosphere, shift to a more efficient remass.

Re: Stun with plasmaI've seen examples of plasma devices where the plasma arc is all jagged, but when you ionize the air with a laser, it tracks on the beam. So the laser part of the stunner may only be a low power guide beam while the plasma is produced by some other mechanism. Another stun method is to use microwaves to cause a nausea ray.

Re: Stopping powerI think you'll find that lasers don't have any stopping power. Yes they burn holes in things, but there's no kinetic energy transfer. And once you fry the nerves and self cauterize the wound, a charging person may not even notice the hole in his chest except from the weird smell.

I concur with Sabersonic's above 5) in regards to limb/organ replacement. Technology is good enough now that I'd be surprised if we couldn't regrow body parts to order (from your own DNA) in 20-30 years. Cybernetics would probably be in the realm of emergency stabilization and willful enhancement, with the possible exception of poorer societies that can't afford to grow tailored organic replacements, but can afford to stamp out mechanical/synthetic-organic body parts.

"Re: Stopping powerI think you'll find that lasers don't have any stopping power. Yes they burn holes in things, but there's no kinetic energy transfer. And once you fry the nerves and self cauterize the wound, a charging person may not even notice the hole in his chest except from the weird smell."

Lasers do afford some advantages in shooting exactly where one is looking. So SWAT assault team breaching the wall to free the hostages probably pack slugs for the sure take-down, but the SWAT snipers on the roof across the way have laser sniper rifles because they know what they hit when they pull the trigger.

Citizen Joe:Your description of Stun Plasma sounds awfully similar to Electrolasers which, if I remember the techicals correctly, only operate in an atmosphere (presumably a thick enough atmosphere to conduct said plasma arc). The PEP style stun setting creates the plasma burst at the point of impact, regardless of atmosphere or not.

Also, Stopping Power =/= Damage. Gotcha, though I figured that damage wasn't descriptive enough to describe the energy delivered to a target. Though I may have to disagree with your description of laser wounds being "clean" in that the wound is cauterized and the nerves fried. From what I've heard, bullet-like laser wounds will be just as bloody as conventional solid rounds and the pain would still be present if not just the nervous shock of being shot.

Re: LasersYou've also got 'Dazzle effects' by shining your laser into someone's eyes or simply blinding them with a little more power. The latter is currently against the Geneva Convention.

Re: Trojan pointsYou should note that Trojans aren't gravitationally neutral. Orbital velocities are another part of the equation.

The alien wormhole tech in my setting naturally migrated towards the largest gravity well, but then opened at a gravitic null. A saddle point where the gravity gradient was zero. Once in system, they could project wormholes to within sensor range or leave beacons, to which inbound wormholes would track. Through blind dumb luck, the humans had brought back the Cancri V beacon for study and since it was on Earth (and not in space) the wormholes couldn't form and the active beacon dragged any attempted wormholes to it. Thus Earth was spared the invasion.

(2) Without going into detailed calculations, the dependence of electrostatic bloom on mass is hard to guess. Heavier particles will end up going slower for the same amount of accelerating voltage (or, at relativistic speeds, will have less time dilation), so they will have more time to be repulsed; but they will also be repulsed slower because of their heavier mass.

(3) Positrons seem rather useless as weapons. It is quite trivial to get electrons up to ultra-relativistic speeds. An electron accelerated to 100 million volts has 200 times its rest mass in kinetic energy. A positron accelerated to 100 million volts also has 200 times its rest mass in kinetic energy, plus another 2 from the annihilation of the positron with the electron in the target. The positron thus only gives you 1% more energy. Compared with the difficulty in storing and injecting positrons, plus your limited supply (lower beam current), you might as well just use a simple electron injector and make your accelerator 1% longer.

(4) If you shoot a 7.62x51 mm NATO round, it will have a bit more than 3 kJ. So you can choose a projectile weapon with more oomph than a 3 kJ laser. The difference will come down to other factors - how much does the laser weigh compared to the battle rifle? How much does a 20 shot battery pack weigh compared to a 20 round magazine? What is your cyclic rate of fire with the laser? Does the laser have a major logistics advantage since you can recharge it on household electricity? How rugged and reliable are your lasers? How accurate (probably extremely accurate, far more accurate than a slugthrower, but it is a question that will be considered).

Personally, I think the pulsed energy projectile idea is a load of bunk - but hey, you're doing space opera with space fighters and mecha. Am I going to complain about lasers with stun settings? Hell no! it's part of the genre.

Re: AntimatterThere are lots of varieties of proposed antimatter rockets. These range from antimatter pion drives, where you annihilate antihydrogen with hydrogen and use the pion exhaust as thrust (good for interstellar missions) to antimatter thermal plasma thrusters, where you heat a plasma with antimatter annihilation off heavy atoms and spit the hot plasma out the back as thrust (better at high acceleration)

Re: Neutron radiationI work in the Radiation Detection and Nuclear Sciences department at Pacific Northwest National Laboratory as a nuclear physicist. I have a bit of professional experience with radiation shielding. In my professional opinion, neutrons are nasty little buggers. And no, they are not easier to shield against than gammas. Especially not the 14.1 MeV neutrons from D/T fusion. The shielding requirements are different - are best shielded with heavy elements. Neutrons are best stopped with light elements, particularly hydrogen, except at high energies (above 10 MeV or so) where you first want to slow them down with inelastic collisions with iron, and then stop them with hydrogen, and then absorb them with boron (more or less - I'm glossing over a lot of details here). And then, in the process of being stopped, they spit out gamma rays from capture and the inelastic collisions, so you need an additional layer of heavy elements behind all that.

Re: Stun with plasmaA jagged arc indicates a flowing electric current - the plasma is secondary to the current flow. Lasers do not guide plasma very well, although they can do a good job of guiding electric dischargeshttp://www.teramobile.org/teramobile.html (down near the bottom of the page).A reasonable sci-fi stunner is an ultra-short pulsed laser that ionizes a wave-guide through the air that directs an electric tazer-like discharge.

The non-lethal microwave devices generally work by causing intense burning pain, rather than nausea.

Re: Stopping powerI disagree. A hole drilled by a laser over combat time-scales will not cauterize, and the fried nerves will scream in just as much pain. This isn't surgical neatness, here - this is lasers whose intensities are so high that they flash skin and meat and gristle and bone into super-pressurized gases that jet out at supersonic speeds, ripping out additional material in the process and producing so much pressure in the wound that the hole blows out like a balloon. And we're not even getting to short-pulsed lasers, that explode like a series of cherry bombs inside of the target. The results will be messy and bloody and painful.

Luke:(2) So basically the amount of electrostatic bloom between Sub-atomic and atomic particles isn't too measurable since it effectively balances it out. Still, Electromagnetically neutral discharges would be more preferred.

(3) Actually I'm thinking of the more "boom" quality of the product, as in a bomb or warhead. There is the idea of impregnating particle beams with positrons but something tells me that's just a bad idea to begin with.

(4) Wasn't really planning on Laser Small Arms being a successor to the more conventional bullet slingers, rather then a competitive choice for infantry where each has its own strengths and weaknesses to the other. One chief advantage of Laser weaponry over conventional is the noticeable lack of brass casings flying all over the place. The advantage of conventional rounds being higher rate of fire due to heating concerns.

After about four centuries of development to Laser Small Arms from Squad Assault Weapon scales and larger, I think it's safe to assume that Laser Projection Small Arms are comparable to standard slugger Small Arms in terms of total mass and ruggedness to both combat and the infantryman themselves.

Chief disadvantage of DEW Small Arms in my setting would be attenuating damage potential over distance, ballistic arc fire and air-burst to which conventional ballistics and solid projectiles excell at. Not really sure if "Shotgun" spread-like damage can be accurately duplicated into DEW format, but I'm guessing that it's a "no" in that department in just technological complexity alone.

"There is something vaguely sinister about this image from Astronomy Picture of the Day. Vast and backlit it glides through the black immensity of space as it has for eons, its shape vaguely suggestive of an ancient, battered ship. If anything is suggestive of the ever popular killer asteroid, this is it."

(2) It's not so much that it isn't measurable, as that I'm not sure which way it will go without doing a lot of work, thinking, and calculations. But yes, electrically neutral beams will be better for zapping things in space.

In air, it is a lot different. Electrically neutral beams will scatter a lot. Beams of one kind of charged particle will undergo what is called "self pinching", meaning their magnetic field holds them together while the screening effect of the plasma they create from the air neutralizes their electric charge (in essence, the charge migrates out to the outside of the beam-created plasma). However, charged paricle beams in air have various instabilities, where the current from the beam interacts with the plasma it creates and the magnetic field it creates to cause the beam to wander unpredictably. There may be ways around this - for example by shooting out pulses so short that they "run past" the disturbance before it happens, but so far it has been a major hurdle in the propagation of atmospheric particle beams over any kind of distance.

(3) Ah, in terms of antimatter explosives, again positrons have the problem of not individually carrying a lot of mass (hence low energy) and their mutual electrostatic repulsion (so you can't carry very many of them). Compared to anti-protons alone, an equal charge of positrons will provide 1/2000 the energy to the target. In the form of anti-hydrogen, positrons will provide 1/2000 of the total energy of the boom, and you will be able to carry a lot more of it.

(4) As I see it, the advantage of a laser small-arm is its unbeatable accuracy. The beam goes where it looks like you are pointing it. No windage, no drop due to gravity, and if there are atmsopheric lensing effects that distort where it looks like where your target is, those same effects will distort the beam the same way so it hits as long as you put the cross-hairs where you see the image of the target. In addition, you will need to add so much electonic beam pointing paraphinalea (adaptive optics, autofocus) anyway that it will be trivial to add image stabilization tricks, allowing even a novice to hold his aim rock-steady.

Plus, a beam that can drill through a man can punch through significantly more armor than a projectile that can drill through a man. A 7.62x51mm NATO rifle fired from a typical battle rifle can drill through 65 cm of ballistics gelatin. Certainly it can smash its way clean through a person. That same bullet can penetrate a bit over 1 cm of steel, or a bit under 2 cm of steel if it is armor piercing. Estimates fromhttp://panoptesv.com/SciFi/DamageInstant.htmlgive 60 J pulses focused to less than a centimeter and delivered in a burst of 50 pulses spaced 10 microseconds apart will drill a 1.5 cm hole through 35 cm of meat (a bit more than the depth of a human body), and possibly leave torn, bleeding, and crushed tissue out to about 3 cm from the primary hole (total diameter of damaged tissue, about 7 cm). That same beam will blast a 0.4 mm hole through 10 cm of steel (well, for this performance you need to focus to less than 0.4 cm), possibly driving cracks of permanent deformations out to 0.7 cm. For more continuous beams, estimates fromhttp://panoptesv.com/SciFi/DamageAverage.htmlhave a 1 cm wide, 1 MW beam with a 0.05 second duration burning a 1 cm deep hole through a 25 cm thick person, with the supersonic jet of evaporate quite likely widening the hole as it blasts out. That same beam will burn a 1 cm hole through 4.4 cm of steel.

Luke:(2) I had figured that Particle Beams, or "Bolts" to be a bit more accurate, would be more suited for orbital and vacuum environment combat. Then there's the little radiation issue that Particle DEWs present that might make the deployment of said weaponry into non-vehicular and non-craft combat problematic at best. Granted, it does give an additional excuse for Full Environmental Combat suits.

(3) So pretty much Anti-Hydrogen makes for the better "boom" in the category of explosives. Now I'm starting to wonder exactly what applications Anti-Protons and Positrons could be used for.

While we're on the subject of explosives, exactly what kind of explosive charge is required to make grenades and air burst rounds a credible threat to power armor. Something tells me that said fragmentation would have to travel at least hypersonic velocities and there are some explosives that already propel shrapnel at supersonic speed and yet do diddly squat in terms of armor penetration.

(4) I'll take it that even with Solid-State phase-locked semiconductor laser diodes, there's really nothing to prevent the implementation of a Reflex Aim-sight upon the Small Arm itself as described in Atomic Rockets.

Citizen Joe:With at least four centuries of Laser Weaponry development, I think it wouldn't be too much of a stretch to postulate the actuality of man portable Laser Weaponry. Granted, in this setting of mine, pistol and handgun ballistic sluggers are still the only choice in the category.

I am going to guess that it will be more efficient to use electrical energy to power a rail or coilgun type weapon for the infantry than a man portable laser. Kinetic energy is also more difficult to defend against (while a laser can be disrupted by fog or dust clouds).

Lasers will be valuable as support weapons, but to get the maximum line of sight, they should be on an airborne or orbital platform. A high platform also has a wider field of view, to better employ the range and speed of a laser weapon. A large platform can also carry larger optics and more energy (however it is generated) than a man portable or even "tank" mounted laser. Given the weather limits of lasers, airborne kinetic energy weapons should also be provided as a compliment.

Once again, we should be thinking about how this affects the people in the story we are telling. Even infantry soldiers do not spend a lot of time contemplating how their weapons, radios, GPS receivers, trucks etc. really work; they do care a lot that the items work reliably and don't require a lot of time, effort and energy to use or maintain. An infantry soldier with access to a laser or coilgun weapon patrolling overhead might feel pretty cocky, while the enemy will be wondering how to avoid being seen and targeted. Political leaders will wonder how few of these weapons they can get away with buying and deploying (or how much they need to overwhelm targets protected by such systems) and taxpayers will have their own views about what they should be paying for.

Thucydides:"I am going to guess that it will be more efficient to use electrical energy to power a rail or coilgun type weapon for the infantry than a man portable laser."

Something tells me that it takes alot more energy to propel a ferrite object to weapon velocities via electromagnetism than laser weapons. And even if that isn't the case, there's the whole issue of recoil upon the individual soldier who might find the bones in their shoulders shattered by the force alone.

Though I do agree that kinetic energy impacts are a bit more difficult to defend from than most forms of DEWs, and that's not counting orbital velocities.

Coilguns are pretty efficient, by my understanding, but and are a probably successor to chemical powered slugs if the power issue makes satisfactory progress (which it will have been if lasers are also in use). Coilguns, however, have the same limitations as chemical slugthrowers: they are affected by wind and gravity, and they take time to get to their target.

Lasers have none of these problems.

That being said, I'll echo Luke to say that it's not "slugs vs. lasers" that's like saying "slugs vs. explosives". A US infantry squad has access to both chemical slugthrowers, chemically propelled grenades, and thrown grenades. There's no reason to think that lasers wouldn't also be in the mix. There are times where they have huge advantages (sniping), and there are times when they won't be optimal (smoke).

As far as recoil is concerned, recoil on a coilgun will be largely the same as recoil on a similarly powered chemical slugthrower (mass * velocity = mass * velocity). Now that I think about it, it might even be a little less, since you don't have to accelerate the propellant also.

Regardless of recoil, the main advantage to coilguns and lasers over conventional arms might be supply lines. Lasers don't need ammo, only power, and coilguns don't need propellant, only power and a slug, allowing each individual trooper to carry much more in the way of shots/kg. While they still need to get power, the advantage is that they can get power from anywhere; beamed microwaves from orbit, vehicle generators, electrical grid, fuel cell, whatever.

I'm going to reserve judgment on the feasibility until someone throws up specs for a modern day laser capable of those effects. From that, we can miniaturize and figure out plausible sizes. My first thought is that if you can pack enough energy for such a laser into a pistol, then you would be able to power a Mack Truck with the same tech. So it isn't a question of can it be done but rather what are the side effects?

Of course not. No one will be sure until one is actually built, and even then it will not tell us how much better such a device can become.

"I'm going to reserve judgment on the feasibility until ..."

Which, of course, we all must. However, for the purpose of writing science fiction, it is entirely plausible, although not certain, that practical handheld laser weapons will exist. Given such an assumption, we can ask what the likely effects of the beam will be.

"My first thought is that if you can pack enough energy for such a laser into a pistol, then you would be able to power a Mack Truck with the same tech. So it isn't a question of can it be done but rather what are the side effects?"

You could, but not necessarily for very long. The design parameters are rather different.

For example, lets take that antipersonnel pulse laser I wrote about earlier. It has a total beam energy of 3 kJ. Since I assumed it was made of phase locked diode lasers, and since high power diode lasers have been demonstrated at more than 60% efficiency, let's say that it draws 5 kJ per shot. Let's give our infantryman a 500 kJ ultracapacitor pack, to give him 100 shots between recharges. Cutting edge ultracapcitors have a specific energy of 100 kJ/kg, so this gives us a 5 kg pack for the ammo.

A Mack truck draws somewhere between 300 and 600 HP, or 225 to 750 kW. We'll take the Mack MR600P series truck, with 300 HP (225 kW) and a curb weight of about 14,000 lbs (6300 kg). If we rip out the engine, fuel tanks, transmission (electric motors don't need gears), drive shaft (put an electric motor directly in each powered wheel), and assorted support gear for the power train, let's assume this counts for more than half of the mass, say 4500 kg. If we assume 500 kg for the electric motors and 4000 kg for an ultracapcitor, we have 400 MJ available. This will be exhausted in half an hour of driving. At 60 mph, this would give a range of 30 miles between recharges. This can be useful for hauling stuff around town, but not for long hauls across the country.

For transportation, what you want is a high specific energy, and specific power is not so important. For beam weapons, a high specific power is paramount, and you can get away with a much lower specific energy.

Having said that, I expect that electric vehicles will become competitive with piston engine vehicles for long distance travel in a decade or so, and will be commonplace on the roads within two decades.

(3) Positrons are useful for medical imaging and a probes for various forms of active measurement (for example, by measuring the shift in annihilation energy with material properties).

Armor is really good at deflecting explosive fragments, but poor at protecting against the overpressure (blast) itself, at least for armor you wear as opposed to armored vehicles. If you intend to use explosive ordinance as an area attack against armor, you will probably want as energetic of an explosion as possible without worrying about fragmentation. Of course, explosives can be very good against armor in the form of contact explosions, where a properly shaped warhead can send a jet of copper from a Monroe effect explosion lancing forth at up to 6 km/s - fast enough that even the strongest material flows out of the way like a fluid.

(4) I would expect reflex aim-sights to be standard on all laser weapons.

The relative energy of laser and coilgun small-arms depends a lot on the details of the laser.

For coilguns, the parameters are easy enough. A coilgun is a linear electric motor, and modern electric motors can easily get 85% to 90% efficiency at turning electric energy into mechanical energy. A 5.56mm NATO bullet is quite efficient at killing with 1.7 kJ of energy, so we can figure 2 kJ of energy per coilgun shot for an effective anti-personnel weapon.

Railguns are like coilguns, but much less efficient - about 30% efficiency (which, oddly enough, is also roughly the efficiency of modern gunpowder weapons at turning chemical energy into kinetic energy of a bullet). This gives about 5.5 kJ per shot for a railgun.

I had previously given several estimates of the beam energy needed to incapacitate a human, primarily by the mechanism of drilling a hole all the way through him. For a laser capable of high energy pulses, I estimate a beam energy of 3 kJ. This is assuming a maximum 20:1 aspect ratio of the hole a laser drills. If you can drill narrower holes, the energy requirement goes down - fiddling with the parameters in my pulse laser calculator I can get 30 cm deep holes with only 1.5 kJ (10 J/pulse, 150 pulses, 10 us between pulses). If you need to use a continuous beam, the energy is closer to 50 kJ. Also unknown is the efficiency. High powered diode lasers have been demonstrated with efficiencies over 60%, and 85% is perfectly reasonable in the near term. However, modern diode lasers have poor beam quality, so that they are used to pump solid state lasers. Diode pumped solid state lasers have efficiencies of about 30%. Going a bit farther in the future, there is no reason a free electron laser could not have efficiencies that are arbitrarily high with room temperature superconductors and energy recovery linacs and injectors. Estimates for the wall-plug efficiency of near term free electron laser weapons runs at around 30%.

Therefore, depending on your tech assumptions, an anti-personnel laser might draw between 1.5 kJ and 170 kJ. The lower end is competitive with coilguns and railguns.

As far as protection, I don't think it is a matter that kinetic slugs are more difficult to defend against than lasers, but rather that they will be defended against differently. As noted, aerosols can be used to scatter lasers, but if we assume lasers good enough to pierce a man through, lasers will be more effective against armor that projectiles.

There are several options for fiddling with recoil. If you go to higher velocities, there is less momentum transfer and thus less recoil for a given energy. This leads to all sorts of trade-offs, though, both beneficial and detrimental. A faster bullet will be lighter than a slower bullet of the same energy, and will be more affected by atmospheric drag (shorter range) and will tend to deflect more when encountering obstacles (a heavy bullet will tend to punch straight through, while a light bullet can be deflected by bones and the like, and take unexpected paths through the target). The lighter bullet will be more effected by wind, but have a flatter trajectory due to gravity. And, of course, a soldier can carry more lighter bullets. For the same energy, a lighter, faster bullet will tend to have less penetration, although this is tricky to estimate and depends a lot on the mechanism of energy transfer to the target.

Thank you Luke for quantifying my top of the head estimates. In the near term, coilguns will have quite the advantage over laser weapons (at least until the energy efficiency and beam quality issues are overcome). As a sort of bonus, a coilgun could be designed to be a multipurpose weapon with a shotgun sized bore to fire miniature grenades or a case full of flechettes, and (perhaps) using the magnetic field to suspend a "bullet" sized bullet when firing at individual targets. A sabot carrying one or more bullets could also be used (firing multiple bullets at once or several rounds in very rapid succession was investigated in the 1980's as a means of giving the infantryman a better chance of hitting a target in battle conditions, and the HK G-11 and "Salvo" round were two separate results of the program).

Using chemical explosives against armour is old technology; shaped charges date to the Second World War (using the energy of the explosion to invert a cone of metal and accelerate it to @ Mach 25 to pierce armour. RPG's and similar hand held weapons use this principle. Tanks use HEAT rounds and anti tank missiles also use this technology). Near the end of the Second World War, "Squash Head" projectiles were developed, which move at a slow speed to "paste" the explosive on the target, a fuse in the base of the round detonates the explosive and the shock wave travels through the armour and rips off scabs of metal and projects it around the interior. Fittings like radios and other things bolted to the inside also tend to be torn off and join the flying cloud of armour fragments. British tanks still use this (in 120mm HESH shells) and so called HEP (High Explosive Plastique) grenades for rifle and automatic grenade launchers also use this principle.

As for lasers, I strongly suspect the critical factor is the optics, so a stabilized turret or mounting for the beam expander mirror (and adaptive optics to compensate for atmospheric effects)will be a "must have". A man portable laser might resemble an anti-tank rocket launcher from the outside; a big tube the soldier lifts to the shoulder to fire, with the optics inside the end of the tube and the laser mechanism somewhere in the middle. For power, the soldier either wears a backpack full of capacitors (be careful crossing the river!), or if the mechanism is very rugged, an MHD generator powered by a chemical charge is in the back of the tube. Load the "round", aim, pull the trigger and an almighty BOOM and backblast of hot ionized gas comes out the venturi while the laser beam shines from the front. The practical limit is the diameter of the tube; few soldiers would carry something bigger than 90mm in diameter (in US history the biggest man portable weapons of this type were a 75mm recoiless rifle and a 3.5" Bazooka).

If I recall correctly, Coilguns are very capable of performing high volumes of fire over railguns (not really sure if the velocity could be adjustable with coilguns or any other type of Gauss-type weaponry) but are not efficient at range vs. volume occupation as with rail guns. A coilgun would have to be lengthen considerably longer than a railgun design in order to have the same effective range. And no, I'm not talking about orbial combat, but surface combat.

I had originally thought about man-portable Gauss-weaponry such as rail guns, but I was advised from a web article (no idea where) that the recoil alone would be enough to cause injuries to the shooters themselves akin or even worse than elephant guns. That advise drove me to push such Kinetic Energy Weapons and Kinetic Kill Weapons into the vehicle and spacecraft domain though with some ideas such as a Railgun Turret slaved to the movements of a marksman. If Gauss weaponry could be miniaturized for Small Arms or at least Squad Assault Weapon scales, and that they don't have to be powerful enough to penetrate vehicular armor, then I may have to reconsider the whole Gauss weaponry idea for the common infantry. It does give me more rationale to use combination-style Small Arms for the infantry: One being a multi-use Laser, the other being a Gauss Launcher for kinetic projectiles and explosives.

Though I am curios Luke, exactly what kind of "Energetic" explosive are we talking about. I have thought about contact explosives akin to HEAT rounds on Tanks, but I was thinking something when a soldier needs to have an explosive to detonate at a precise distance when a target is hiding behind cover.

OK, now how fast can you dissipate the heat on your focal array? They aren't 100% transparent/reflective which means that some of that energy gets absorbed by your optics and gets converted to heat. Heat will distort the optics which results in less efficiency and more heat gain. For that reason, larger optics are better since you're spreading your energy over a wider surface.

Let's see... Dielectric mirrors can get 99.999% reflectance over a narrow band of wavelengths (which is fine because our laser is narrow band). The mirror will be absorbing 1/100,000th of the output energy... which Luke has provided at 3 kJ. So that gives us 3 millijoules per 'burst'. How small an area can we spread that such that it doesn't damage the optics? That will tell us the minimum optics diameter for 'continuous' fire. Keep in mind that even a minor scratch would be a thousand fold increase in absorption. So the ground pounder may still not be using the MP lasers due to the fragility of the system. Like how the M15? was a superior weapon to the AK47 but it would jam so much and the AK could be packed with mud and still fire.

Welcome to new commenters, and I see that you all have been busy in my absence!

On the image, Prometheus is just going about its peaceful business, but what caught my eye, as it did Bernita's, is the angle and lighting.

Power Transfer Conduit (PTC) technology should not be housed in a black box, but one with bright yellow chevron stripes, and a warning label HANDLE WITH EXTREME CAUTION !!!!!

And that goes double for authors. Not only can you plug into a handy star, you can reverse it to hoover up laser beams. That is one powerful gizmo. Use it, but be mindful that one little slip with it could wreck your plot.

The cost of present day space travel is not about energy - propellant is most of lift mass, but only a tiny fraction of launch cost. What costs is expensive hardware and (even more) launch teams.

On laser small arms, my impression is that the bench or even aimed shot accuracy of the weapon hardly matters under firefight conditions. Aren't troops more often squeezing off bursts at a moving shadow, or to keep the other guy's head down?

Here are some images I made of what a laser weapon designed to be used in the same role as a modern assault rifle might look likehttp://panoptesv.com/SciFi/raygun4.JPGhttp://panoptesv.com/SciFi/raygun3.JPGhttp://panoptesv.com/SciFi/raygun2.JPGhttp://panoptesv.com/SciFi/raygun1.JPGThe laser mechanism is in the stock, with a cooling fan to blow air past it. Power handling equipment is in front of the grip, a reflex aimsight above the grip, and of course the focusing lens is up front. An ultracapcitor (shown) fits in front of the grip. Here's an image of the laser in usehttp://panoptesv.com/SciFi/FireFight.JPG

For a man portable battle laser, emitting 1 micron near infrared and focused through a 10 cm lens, it can hold a focus of a millimeter at up to about 75 meters, 2 mm at 150 m, 3 mm at 225 m, and so on (assuming diffraction limited performance). My estimates for the nominal "assault laser" given earlier (60 J pulses) you will need to focus within 15 mm for optimal performance against flesh, within 4 mm for optimal performance against steel, and within 2 mm for optimal performance against super-nano-carbon armor.

If you can get power supplies to dump energy fast enough, coilguns could in principle give very high rates of fire, because they generate little waste heat (significantly less than modern firearms for the same exterior ballistics). Railguns have serious problems with rail erosion for high speed projectiles, and will probably need to have their rails replaced every few shots (some Navy programs considered treating the rails as part of the ammunition, to be replaced with every shot).

At the moment, we really don't know how compact a well optimized coilgun would be, except that an R&D effort would be much more expensive than for a railgun. Railguns are really quite simple, coilguns would need high speed switches for inductors and other expensive stuff.

There is no reason electric propulsion technology needs to have high recoil. A coilgun firing 4 gram projectiles at 1 km/s (the same as modern assault rifles) would have no more recoil than a modern assault rifle. As mentioned, by making the bullet lighter and accelerating it to higher speeds while keeping the energy the same, you can bump the recoil down (with other benefits and costs).

The sorts of energetic explosives I was thinking of is - well, I am not allowed to go into too much detail, but since it is all fictional and well beyond our current technological capabilities, lets just say that it is not unreasonable to have highly compact nuclear explosives as man-portable ordinance in science fiction settings.

I usually figure man portable infantry lasers will have focal arrays on the order of 10 cm across. This gives adequate focusing power, and about 80 square centimeters across which to dissipate heat. A diamond window on the front can help to keep junk out of the optical path that could scratch the lens/mirrors, and diamond is both very transparent and has an amazing thermal conductivity for dissipating heat.

New generations of explosives are in service now which allow 500lb bombs to have similar effects to 2000lb bombs used in the 1990 Persian Gulf War. These small diameter bombs allow aircraft to either go faster and farther (they only have to carry a fraction of the weight), or carry a lot more death and destruction than before.

Various types of thermobaric weapons have also been perfected, the smallest ones I know of are RPO-A infantry rockets Russian troops use in place of flamethrowers, while huge things like the MOAB ("Mother Of All Bombs") rival nuclear weapons in power.

The US Navy is very interested in kinetic energy; the DD-X program had a long term goal of fielding a 64 MJ railgun that could deliver ordinance to a target @ 350km away, the warhead being a hunk of steel moving at Mach 6 on impact (after traveling outside the atmosphere for a good portion of the journey).

The observation that much Infantry fire is used to suppress the enemy is true today, but up until WWI Infantry soldiers were trained to use accurate fire from bolt action rifles against targets 500m distant or more (using iron sights), and volley fire against area targets such as field artillery at ranges of up to 2000m (using iron sights as well).

Expanding on today's emphasis on close range battle and ambushes, Infantry weapons could devolve into shotguns or similar weapons (high tech Metalstorm "Streetsweepers" firing hundreds of rounds in a concentrated burst might be the western approach), and programmable grenades linked to the laser rangefinder on the weapon are in development to airburst over the last position the enemy was seen (ducking under cover won't work so well).

How this might affect the military? We could see a "road warrior" ground force armed with sawed off shotguns and shivs taking positions where they could call in fire from a high tech force armed with long range lasers or kinetic kill vehicles. They might not like these fire support soldiers (zoomies or squids), and indeed they may never even interact with them except through an encrypted radio or text message link (talk about depersonalizing war).

We've already seen relatively primitive ground forces calling in high-tech fire support in Afghanistan, with US Special Forces riding with Northern Alliance horsemen calling in smart bombs on the Taliban.Of course, in a science fiction setting, the short-ranged ground forces could be anything from a colony's militia armed with simple home-made firearms to unmanned ground vehicles just as sophisticated as the bombs, missiles, lasers or railguns serving as fire support.

Citizen Joe:1) I had been thinking that nuclear ships are only available to militaries, and everyone else gets beamed energy for VASIMR and similar systems for orbit-to-orbit operations. Maybe fusion is still common as a launch engine, though?

Love the idea of a Callisto detox center.

2) Excellent. I figure that the ship is only designed to burn when the habs are retracted. Bridge, engine room are micro-g the whole time.

3)Rad-eating creatures will be a big deal everywhere, I think. Cleaning up waste sites, living on some satellites in the outer planets, maybe even with some anti-rad medical uses.

I think that the cephalopod body plan is relatively common in the universe. Same goes for arthropods and vertebrates. They're just too useful.

4)Interesting, though I'm skeptical it would require much space. Computers get smaller over time, not bigger.

5) Makes sense. Room for both, in other words.

6) So in other words, I have a License to Technobabble.

Luke:0) There's a thought. I'd always thought of the ship as fundamentally Martian, but perhaps it was built on Earth or the Saturnalian sphere.

5) That's probably the most common. We'd also see organic stuff and borg stuff. I'll probably add some sort of cyberpunk subculture that embraces the non-human looking stuff.

6)See #6 above :)

Michael:How likely are we to find black smokers on the moons of Jupiter and Saturn? Is there any reason to think that they are or are not present on, say, Europa?

Sabersonic:1) That could work too. It would fit in the the rocket's status as a retro creature right out of the 20th century.

2) Matter of fact, Pilgrim observer was where I got the idea. Mine is a little different--the hab units are just at the end, with a retractable tunnel/frame connecting them to the centrifuge, and there are two instead of three. During a burn everything is flush with the hull, as in the Pilgrim design.

3) It's looking like I can plausibly postulate thermal vents on at least one of these, then. Which I will happily do. Any idea which is most likely? Europa, Ganymede, Callisto, Titan, Enceladus?

5) Printed organs?

6) That could be it. I'm also considering the possibility of FTL travel through gates, as Rick was talking about in a recent post where he likened galactic travel to a mass transit system.

Those laser 'rifle' images are truly wonderful, both plausible and badass looking. Invented tech doesn't get better than that.

The sorts of energetic explosives I was thinking of is - well, I am not allowed to go into too much detail

I think you just outed yourself as involved in classified research.

Since I was a kid I have heard vaguely about nuclear isomer reactions, with an energy release somewhere between chemfuels and 'classic' nuclear reactions. I think they've been discussed on SFConsim-l, but I still know basically nothing about them.

But obviously a bang worth a mere 1000x TNT equivalent, instead of the million or so of regular nukes, would still be quite a bang, especially if it can be arranged on small scales, e.g., a 1 kg warhead packing the equivalent of a ton of TNT.

The political implications are dicey, because losing the current bright line distinguishing nukes from 'conventional' weapons might work out very badly for postindustrial civilization.

I do have a security clearance, because my job sometimes requires me to know about things that, frankly, I'd rather not, and that it is a good idea not to let everyone else know about as well. I try to use my powers for good, however, rather than evil (in particular, nuclear security and safeguards rather than weapons design).

Now, I'm off to Portland for a week, in which my access to the internet may be sporadic at best.

You COULD get this with chemfuel. All you have to handwave is the materials tech to make an SSTO practical. If Super Carbon Nano Stuff can provide a strong airframe at a fraction of the dry mass of current practice, you are good to go.

And once you have a practical SSTO, there is no inherent reason you can't simply refuel on orbit, and off you go again. Chemfuel will constrain you to more or less Hohmann orbits, but you can use the Oberth effect boot, and your SCNS hull can aerobrake.

For regular commercial travel, specialized shuttles and deep space ships are much cheaper, but military and other official missions could call for ships equipped to make the straight jump, needing only to refuel.

As for habs, I'd just spin the whole ship, and winch out the hab modules from each side.

But if you go this route, don't forget other implications of SCNS as a structural material. Bridges will look really scary to our eyes. (You can mostly get around this by saying that SCNS is expensive. We don't build bridges out of titanium alloy, or even aluminum.)

Luke and Sabersonic:"(3) So pretty much Anti-Hydrogen makes for the better "boom" in the category of explosives. Now I'm starting to wonder exactly what applications Anti-Protons and Positrons could be used for."

Well, Positrons could be used as an airburst weapon to create battlefield "death ray" type weapon to kill enemy soldiers and disrupt electronics in rear-echilon staging areas. Anti-Protons could be used in power generation because they produce charged particles as a reaction byproduct...proton anti-proton beams colliding at the mouth of an MHD could be a powerful and compact power supply.

It occures to me that an infantry weapon that combined a multifunction laser and a multiple-feed 'slug-thrower' into its designcould become a standard issue weapon...and then the grunts would complain about the 'do-everything-but-work-well' POS they were forced to use against an enemy that uses a varity of different weapons optimized for different roles...

As far as FTL goes, I only have two things to say:1) when you go into 'warp', you do know that all the heat you generate during the trip will also go with you and the whole amount you have radiated from your ship will be dumped upon 'reintigration' into the normal universe.2) To generate a 'space-warp' using some sort of gravity generator, the ship will mass several billion tons when the drive is at stand-by (just below the spacewarp-creating threshold), and very difficult to propel by most conventional means; in a combat situation when you may need a quick getaway, you will need to 'keep the motor running', thus preventing the starship from being able to manuever quickly(ie, greater than a meter a week), so military starships may very well need 'rider' combat craft (of whatever type or designation) to be effective; if you don't just want to drop into a system and launch a zillion missiles then jump out again, you will need some sort of daughter combat craft.

Taking a current trend and projecting it into the future; why not have Ground Remotely Piloted Combat Vehicles? A teleoperated robot that is controlled by a soldier several miles/kilometers away; perhaps even in orbit. This miniture walking tank could be heavily armored, heavily armed, and effectively tireless (three shifts of soldier/operators make them 'sleepless') limited only by they're power supply, ammo load, and maintenice/damage-repair needs.

A personal nitpick: when I read a Sci-Fi novel or look over the rules/backstory or a Sci-Fi game and see that both the humans and the aliens have the exact same weapons/drives/tech-in-general it just makes me see these 'aliens' as funny-looking humans. Aliens should be alien...the way they look, act, the tech they use, the whole 'feel' of them should be different from the humans. Volcans' may be cool and T'Pol may be hot, but let's face it; we're never going to meet them because they either don't exist, or if they do, they have, did, will evolve in a distant gallaxy that we will probaply never reach.

PTC tech might involve great cost, greater risk, and if (read: enevitably) fail it will be catistrophic...the failure of a PTC would vaporize a spacecraft or a large city.

A rail/coil gun that is used like a large caliber sniper gun; if you brace it against the ground and fire it at long range at armored targets, then it would be an effective type of infantry weapon.

Powering a beam weapon with cartriges would work; multipower setting using cartriges would also work. Either you could use fractional totals of each cartriges' charge, or you could use different cartriges; each of these could deliver a different power level (5.5 KJ, 2KJ, 11 KJ, 60KJ, ect.), with multiple feed weapons.

Re: Laser cleaning practices. Although the heat conductance of diamond and it's heat tolerance make it good as a dust shield, I'm not convinced that the transparency is suitable for lasers. The laser system could be designed specifically for that though. I think that a relatively inexpensive safeguard would be a mirrored shutter that then allows you to send a probe pulse through your dust shield to measure transparency. If your transparency is too low, you get a warning. Likewise if it is really low, the safeties kick in and the laser doesn't fire. I think that it would also be funny to see the diamond market crash when 10 cm defective dust shields show up on the market at regular intervals.

Re: Aliens = Humans + ridges. A very viable rationale for everyone using the same FTL tech is that humans will steal any technology they can... and then sell it as their own. So everyone ends up with the best technology that can be re-engineered.

Re: Computer size. For a given size/price computing power doubles every 7? years? something like that. So when I say that an emergent AI requires massive banks of computers, that should tell you something about how much data is actually required for one. Imagine if you will, that your world was recorded twenty four hours a day for the last thirty years. That's the volume of data that they use to emerge. AI in a robot, not so much, but a robot could be controlled from a ship board AI.

3) Take your pick, though I would have to exclude Titan since fire + hydrocarbons and natural glass =/= ideal environment for life. What with all the mass fires and all. Granted, it assumes some presence of oxygen but I ain't going to take that bet. The ice moons on the list make far better choices since many of them are suspected of having a subterranean ocean(s) beneath all those kilometers of ice.

5) I can't really recall the documentary, but it was basically visualizing what the world would be like fifty years from now and one program focused on medical advances and showed one scientist who injected heart cells into an ink cartridge and turned the printer on. It's not a full heart, but its an interesting innovation none the less.

Not as cool as cybernetic and bionic prosthetics as shown in most forms of cyber punk, but still...

Luke:Well, I feared that it would take an anti-matter explosion to get the desired effect out of a grenade against power armor without resorting too much to contact fuses. But unless I read wrong, it appears that you're suggesting Nuke Grenades.

It almost makes me giddy with joy, but I'd better hold that off for another time. Might not have to make TOO drastic a detail.

Ferrell:For the whole Heat thing, well I figured as much since the energy required to perform a Dive will be exponentially high as is the waste heat. Granted, the time frame within the Warp Conduit through hyperspace rarely exceeds an Earth Minute when performing standard transit.

As for gravity generation for warp, well gravity isn't really generated by the craft for the purpouse of interstellar FTL but rather the stars (an in the case of most military starcraft, planets) themselves. As for the "FTL outta danger" scenario, well that's simply not possible. If it isn't the cooldown rate of the drive after the jump or that everyone practically knows that a starcraft is diving out days, even weeks in advance due to the physics of the Hyperspace Warp Dive, its because the Dive Out point isn't the same as the Dive In point. To be exact, all Hyperspace Warp Dive starcraft dive-in at the polar regions and dive-out at equatorial regions. A quick getaway still requires a spacecraft to accelerate via rockets even if equip with a Warp Drive to enhance performance.

As for your personal nit-pick on alien species having the same FTL as the humans, well that's not gonna be a problem in my setting. There are Quantum Transmission Gates, Tachyon Conversion technology among others. And that's not adding into the antagonist civilization's technology.

Humanoid aliens on the other hand, well it's a work in progress but I'm getting there.

As for the PTC tech, well the only rationale I could think of is energy "bandwith". Or rather there's a certain amount of energy that the PTC tech could collect from the mother star despite its unlimited. The exploding spacecraft due to the power core is pretty much a staple in current sci-fi, so why should this power source be any different? Granted, PTC that powers a city would probably be best placed at an orbital location.

Re: PTC... Don't get me wrong, PTC is a HORRIBLE idea with all kinds of world shattering problems. But the concept does solve many of the problems with the staples of scifi. Fighters, mecha, heat dissipation, reationless thrust, etc. All those go away when you can tie into the grid. Lay down a few rules about how to access it and various safety protocols, then place the technology in the hands of the military and you can neatly side step all the usual hard scifi complaints while limiting the damage. I am enamored with the idea that FTL ends up depleting the host star and thus creates a real concern about the welfare of any busy star systems.

Re: "Emergency jump to hyperspace". This has always struck me as jumping off a cliff and hoping you don't get dashed on the jagged rocks below. FTL fields just seem to be very fragile and complicated. In order to work right, a million things need to go right. All it takes is a fly in the system and suddenly you're Brundlefly.

Re: Different alien technologies. In the setting I was working on, the aliens mastered gravitics which they then used in order to make wormholes. In this case, the aliens consist of many species from many worlds under the control of puppet master aliens from another dimension. Gravitics is just a natural extension for these puppet masters and thus they develop the gravitic technology without their slaves actually understanding it.

Terrans discovered their own means of FTL accidentally as part of total mass conversion experiment. Orbital LHC-esque power generator lab goes online and disappears in a flash of gamma rays. Project is abandoned. Decades later when first gas mining operations reach Jupiter, the hulk of the lab is found in orbit. The Terrans then go on to develop the FTL tech from there. Ironically, the Terran FTL drive severely messes with the alien puppet master's dimension like using an Orion style liftoff in a protected wildlife sanctuary.

On printable organs: Tissue printing produces biological constructs that are homogeneous, because the printer cartridge is loaded with one or a very few types of cells, so you can't get the extended complex structure in most organs.

As techniques get better, this might improve, but my gut says that even if you can accurately lay down many different kinds of cells together to make an organ facsimile, it will be more difficult to make organs that are under some tension. I'm thinking specifically of the heart and skeletal muscles, because each cell in muscle is very long and interconnected with its neighboring cells much more thoroughly than normal cell-cell adhesion.

Grown organs don't have this problem, because the organ is coming together in a more "natural" way. Although it may need to be stimulated during the growth process to make it grow properly, electrically stimulating a vat-grown heart to pump a saline solution seems easy compared to growing the heart in the first place. Vat grown organs would likely take a bit of extra time over printed organs, though.

I'd say that Enceladus is a great candidate for thermal vents, because we have observed geysers currently active now on that moon.

That being said, it doesn't take black smoker style thermal activity to allow life, you don't need to go to hundreds of degrees C to get life, you just need to get above the cripplingly cold -160 C or so of the Titan surface. I don't know what a lower limit for life would be, but the presence of liquids is important, because liquids allow molecules to interact much faster than solids, making life a lot more likely.

I have no beef with PTC as an operatic tech! I'm only cautioning that anything that powerful risks the Trek transporter fail if its implications aren't thought through in advance.

On alien technologies, this is a big can of worms, and I have mixed feelings. On the one hand, technologies that arise out of entirely different traditions should be different. On the other hand, the laws of physics are the same for all races, and Ma Nature usually favors certain ways of doing things.

Ideally, I think you want something equivalent to an encounter between Chinese treasure junks and European galleons. Both use the same basic technology, wooden hulls driven by sails carried on multiple masts. But nearly every detail is entirely different, representing a parallel design solution.

This is where a writer really gets the benefit from this thread/website. You don't have to come up with two (or more) plausible technologies for the same situation, you just posit the situation and let hordes of technerds do the work for you :)

On TPC... I would hazard a guess that the 'conduit' is some sort of subspace directional beam that possibly loops back to the largest mass in the system, i.e. the host star. Only protons and electrons can be transmitted in the conduit and the neutrons get shed at the injection site. That's probably a nasty neutronic radiation site. If you can sync up with the conduit with your own field, you can dump energy into or pull energy out of the proton flow. Lasers energy would thus get dumped back into the proton stream just like you'd dump waste heat. If the proton stream is too energized, you can't dump heat/energy into it. If the stream too low on power then you can't draw energy from it. If you draw protons out (to recreate your reaction mass, or FTL jump mass) then those protons aren't available for the next guy in line. It is sort of like running a power grid. You have to time your generators to produce power when the peaks are reached but not so much during slow times. Obviously, destroying the projector station would cripple many vessels, but getting to the projector is nigh impossible and firing lasers at it would just charge it up a little more.

Stripping neutrons is a good way to prevent abuse of the system since it basically limits it to hydrogen transport. It does make travel to older stars more difficult since they would have already burned up all their hydrogen. But I'm not sure how much interest there is in the non-hydrogen stars.

Delta wings are nice, but I like what I consider to be the more classic rocket look. My favorite aspect of the Tintin rocket are the fins with the shock absorbers on the bottom.

Interesting thoughts re: chemical rockets. I'll probably make it out of Super Carbon Nano Stuff regardless. What would the scary bridges look like, and how long can they feasibly be? I like the idea of a bridge spanning the Taiwan Straits as an example of the crazy engineering they've got in the 22nd century, but I have no idea what the SCNS is actually capable of.

I have also thought of spinning the whole ship as opposed to a centrifuge. I go both ways on this one.

Incidentally, I really like the Zeng He vs. Magellan metaphor. I tend to favor the absent aliens trope (not that they're not out there, but it will take some time to meet them and there's a lot of untapped stuff in this solar system). Eventually though, first contact happens and the extras deserve good treatment.

Sabersonic: Ok, Titan's probably out, then. I'm thinking teeming life on the sea moons provided they've got vents. At least one of them will--the possibilities are too interesting and if they actually find life I can say, "called it!"

Sounds like an interesting documentary. 21st is definitely the century of biology. Not that we won't see the cyberpunk stuff either--I'll probably include both.

I'm wondering what is everyone's opinion on how easy FTL travel should be. For example in the Stargate setting, FTL is pretty easy through the gates. I'm surprised they didn't whip out their iPhone near the end there and pull up the gate with an app. In other settings, you've got restricted locations to jump from like the poles of a star.

I tend to favor the difficult calculations philosophy but safe so long as you follow protocols.

I've been in favor of making FTL relatively reliable, but with some serious limitations.

I also don't like FTL to be particularly near points of interest, requiring long burns of more traditional rockets. I've never been a fan of just popping into orbit.

I prefer to have FTL points be out of control of civilizations. Either naturally occurring phenomena, or some sort of discovered ancient magitech that can't be replicated...if we can't control the location, that solves the "railway wormhole on a planet" problem that obviates the need for real space travel.

That being said, I think there's plenty of interesting stories to be told in the solar system. The only real reason to leave it is to have Earth-like planets and blue alien babes for our heroes to sleep on.

On FTL Reliability:Well, to sum my feelings on the subject at hand, a quote from Atomic Rockets explains my position perfectly

Brett Evill- "These start-anyway go-anywhere drives play merry Hell with concepts like 'distance', 'remoteness', 'proximity', 'adjacency', 'line of communication', 'border', and 'defence', while reinforcing such concepts as 'trade', 'concentration of force', and 'first strike'. Give me a setting in which the map still matters."

To be exact, FTL should only be reliable in getting from one star system to another and that only a few government organizations should be able to perform IP FTL. Everyone else has to slog it out conventionally via rocket engines. This makes combat a bit more dramatic and rationalize "run and gun" style of retreat where the commander of the starcraft has no choice but to fight to survive the trek to the nearest jump point to escape the hostile star system.

Another possible limitation is the ol' so reliable power restrictions. That is it takes so much energy to charge up the drive that it's impossible to fire your more devistating Directed Energy Weapons at the same time. Instead the combat starcraft is limited to Missiles and possibly Kinetic Kill Weaponry.

MRig: The documentary is a series called 2057. I'm sure there are some video clips on YouTube, if it's working that is.

On PTC Tech: While I like the idea of broadcast energy gathered from the star (just not the part on "reactionless drives", I've been warned to avoid them like the plague), PTC as it is described does have its downsides and does question the existence of both Fusion Reactors and Anti-Matter Reactors. One possible way is to explain that the PTC grid can't power itself and requires said reactors. Probably best to downgrade them to over glorified solar electric sattelites that can broadcast their "beamed" energy to recievers. Granted, it does leave alot of political and economic to the electrical company that builds and maintains them, but a space opera (especially one with some Hard SF elements) might as well have at least one Mega-Corp in its setting.

On Alien FTL Tech: True, physics as we know them is a little finicky in how a certain design of technology operates. After all, a rocket is still a rocket no matter how the remass is accelerated but even then it comes in so many different flavors from the old stand off chemical to ion, plasma like VASIMIR and even torch drives of fusion and anti-matter to even Orion. It could also be one reason why FTL is difficult to achieve in that it can be generated in a number of different ways, ways that may not be so compatible with one another.

I have three ideas for FTL:1)a tech that uses an extracosmic connection between distant points(interstellar) and 'displaces' them, i.e. instantaniously swaps one bubble of spacetime with another...and all the mass and energy imbedded in those bubbles of spacetime.2) a spacewarp drive that uses two gravity generators; they amplify mass by spinning bubbles of cold plasma at near light speed on all three axies...it takes several hours/days/weeks to spin them up, depending on the power plant type used.3) a hyperspace access field generator with navigation through hyperspace being accomplished by a human directing the ship's course via a kareokie type interface (instermental, vocal, or both*)...

The problem I see with the bubbleswap FTL is that the two points are likely to have nowhere near the same velocities. For example: If I bubbleswap from one side of the Earth to the other, I would find myself moving at mach 3 relative to the stationary objects there. This only gets worse when applied to interstellar distances.

I've seen this Welsh singing thing a few times now. I'm not sure of the reference. However, it seems to me that hyperspace or whatever is going to be non-euclidean and thus really going to freak your brain out to look at it. If instead of a visual interface, you listened to the sounds of your protective bubble rubbing against the hyperspace conduit, you could get more dimensional information from sound than visual. Then, you stick someone with a good ear at the helm to adjust the course and tune the trip. As a woodworker, I can tell when there is a problem by the sound of the tools long before there is visual evidence of a problem.

If I were you, Rick, or many of the other commenters on this blog I would keep FTL to a minimum: you(s) have the math for a good hard sci-fi battle and I would think prevalent wormholes or other FTL would cheapen that battle (especially if such tech could be used as weapons). If you do have FTL I would make it exceedingly expensive perhaps connecting it somehow to antimatter and its cost: Perhaps you could make FTL viable and cheap enough to jump a fleet into battle somewhere past the heliopause of any given star system once per month or year or somewhere in between (perhaps a star’s gravity would/could destabilize a nearby wormhole- ask Luke about that). This way you could employ the tactics of lasers, rail/coil guns, nukes, ASATs, etc. in another star system while still maintaining an engrossing hard sci-fi space battlefield that would otherwise be restricted to one’s own star system because of sub-light speeds. Funky Aliens and Hard Sci-Fi! Fantabulous!

I want to do a Hard Sci-Fi Novel and in fact I am working on one (as I was inspired by this blog) but I know am hopelessly outgunned when it comes to the numbers (I used to be good at math but now I revile it), so for me magitech may be the only way! Does Winchell Chung do any tutoring?

-What if there was another ‘primitive’ space ship inside the other bubble of the bubble swap? That could make for a good story right there: We are sending out or first manned mission to Alpha Centauri and POOF they are gone, disappeared to God knows where. . . and in their place. . .

After looking at Luke's images of his Assault Laser on Atomic Rockets and reading back on said website's info on laser small arms the other night, I got this interesting though potentially stupid idea on the heat management.

If a single round of laser energy, or to be exact the series of pulse that delivers the damage and I have a feeling that CW beams are too problematic, produces little to no more thermal energy then the equivilent ballistic round then what's to prevent a designer to have the heat sink in the same magazaine as the laser energy capacitor?

As a system that would augment the existing coolant system (at least), it would be very advantageous in that the heat of all the laser pulse rounds in the spent E-mag would be removed and replaced with a fresh E-mag that has a heat sink ready to be filled once again instead of having the heat build up within the Assault Laser Projector itself. This system would potentially work regardless of the presense of a convecting atmosphere or not. It probably doesn't work as well as my brain fart suggests, but it's an interesting idea none the less.

Though now I'm wondering if it's a technically a plausibly good idea to have modular heat management systems between two modules: one for heat convection in an atmosphere and the other a heat sink for hard vaccums and similar environments?

VonMalcolm:Sounds like the kind of FTL you're proposing as an example sounds like some kind of Space-Time Displacement field not unlike that Temporal Displacement Equipment from the Terminator movies.

Sabersonic: Having a replacable heat sink attached to your laser weapon is a great idea for when you have to use it in a vacuum...but it might be the size of an E-magazine, so you might want to have an additional attachment point for your heat sink.

VonMalcom: Using an FTL that results in the starship massing several billion tons will not allow that starship to move around very well when the 'motor is running'; so just use it as a big truck. Now, if it takes several weeks to 'spin-up' the FTL so you can use it, then you will need daughter spacecraft that use a different tech than the gravity generators your starship uses; maybe something like ordinary rocket ships or wheel-like electric propulsion vehicles, or what-ever-you-want-to-use as your 'normal' spacecraft consellation...

Bubbleswap FTL...I like that! Unless the transfered mass/energy's velocity is relative to the local gravity field, then the transfered items would shoot off, probably at high velocity; so having the Bubbleswap in space would be a really good idea...:)

Having an FTL that needs to use people singing (or playing the drums, ect.), in order to navigate through Hyperspace just sounded too funny to not consider it...

Back when I was dealing with a traditional interstellar setting, my FTL jump points were off in deep space, effectively giving interstellar travel the look & feel of interplanetary travel, just with more planets in reach.

There are a few references in comments to making FTL fabulously expensive, but there is a hitch. If the whole purpose of FTL, in story terms, is to put a bunch of nifty colony planets in reach, the implication is that interstellar travel is cheap enough that these planets could be colonized in the first place.

Ferrel:Initially, it'll probably be a separate component to the E-Mag since it's a completely new system. But I think wouldn't be too much to assume that, over time, the replaceable Heat Sink would be merged with the E-Mag. Granted, it'll probably be a rather large E-mag, perhaps the size of Luke's Assault Laser Projector's E-Mag which I presume is the same rough dimensions as the 20mm grenade magazine on the OICW design.

Rick:Well, the FTL Star Drive shouldn't be too cheap enough for any yahoo to buy and do whatever they want. I believe that Jon's Law should apply to FTL Drives if only because something that harness that much energy for FTL alone should only be in the hands of those competent enough and well trained to use it responsibly.

Though this kinds of means that the settlement of extrasolar colonies would be solely in the realm of governments and big corporations. Then again this has been mostly true of such colonization that date's back to the colonies of Virgina, if memory serves me correctly.

Anyway, I have a few questions that I would like some aid with:

1) Considering that I'm utilizing Plasma "bolts" that fly at relativistic velocities, how does one calculate the maximum effective range of such DEW projectiles?

2) While we're on the subject, how dense should each bolt be compared to the surrounding atmosphere, less, more, about equal?

3) What would be considered the minimum relativistic velocity for said Plasma Bolts? Lasers are 100% the velocity of light by default and Particle Beams can reach upwards to 99% the velocity of light (potentially less, depending upon the size and mass of said particle), but what of plasma bolts?

4) How do you do underlined text in html? Apparently the comment script doesn't accept the "u" code.

FTL:Honestly, my thought isn't to make it fantastically expensive, or at least not much more so than...let's say travelling the breadth of the solar system. Honestly, if we knew there was a habitable planet within...say...2x Pluto flying range, I would venture to say our planet's manned space programs would be SCRAMBLING to get us there.

The beauty of limiting FTL by geography is that you get rid of a lot of random nonsense. If an invading fleet can pop up anywhere, why bother with a fleet at all? Send in a few planet slaggers and pop them into LEO.

Plasma Bolts:My understanding is that plasma bolts aren't considered a very good weaponry basis, because you're essentially firing steam as your ammunition (the bolt will spread and become worthless very quickly).

So, to make the whole concept work, you'll need handwavium to make the bolt maintain cohesion. At that point, handwave whatever speed sounds cool, I suppose. I wouldn't recommend uber relativistic speeds, as a bolt of plasma is fairly massive, but depending on the caliber you pick you could probably work out the number you want.

If you want some STL directed energy weapon...maybe a better solution would be bolts of superheated metal? All the glowiness, less handwave.

ElAntonius:To be honest, after reading both the Atomic Rocket and Stardestroyer.net articles on the subject, I was content on making such plasma bolt castors very short ranged DEW weapons even with a magnetic field extending some distance from the castor barrel to which it dispersed immediately afterwards. In fact, I had a particular classification in mind for DEWs:

1) Lasers - Longest Effective Range, lowest damage potential.

2) Particle Beams - Medium Effective Range and damage potential.

3) Plasma Bolts - Shortest Effective Range, highest damage potential.

However I re-read the article from stardestroyer.net and it concluded that the plasma bolts as seen on sci-fi media as visible "bolts" that travel slow enough for the human eye to register yet have a flat trajectory akin to a laser was not physically possible. The article suggested that the bolt could potentially travel at relavistic velocities to keep its coherency at a reasonable combat distance and keep coherent long enough to deliver thermal (and possibly some kinetic and or electrical based) damage. Velocities that, to the human eye, would make the traveling plasma look more like a "beam" when it is actually a "bolt" in nature and form.

And with a proper bolt density (still haven't really recieved the answer on the bolt's proper density), the plasma would have a noticably curved trajectory in the viewpoint of the shooter: Not as flat as a Laser or particle beam, but not as ballistic as conventional bullet rounds and still takes some skill to take into account the numerous variables that would affect the bolt's trajectory once it leaves the system proper until it reaches its target, intended or not. The Bolt may be considered firing steam, but this puff of steam burns at high enough temperatures to at least structurally weaken metal. Lasers are essencially beams of light as well yet weaponized lasers can still cause considerable damage upon impact even today.

I think that one possibility for a plasma bolt weapon is to use the charge differential as a guide path. So you basically shoot electrons at a target until he becomes suitably charged, then discharge a plasma bolt which homes in on the target.

Or you could charge up your target and launch a energized chemical which detonates when it hits the charged target. It is like superheating water beyond its vaporization state then changing the environment so the whole thing snaps to steam instantly. Or maybe like throwing nitroglycerin into an open spark. But by maintaining the plasma in a supercharged liquid state you can maintain cohesion long enough to reach the target. Plus you get the cool sound effect from charging up your blob. Beyond a certain range, the chemical drops below the critical range and becomes 'less dangerous'. This makes it 'safe' for use in a ship or station where projectiles tend to cause air leaks.

I didn't mean that a plasma bolt that had maintained cohesion would be low damage...quite the opposite, really. If you could keep the damn thing together, it would be devastating...it combines the damage properties of kinetics and of lasers in many ways.

Note, I can't get to stardestroyer.net from work, so I haven't read the article.

If it is indeed possible to maintain sufficient bolt cohesion at usable range via massive speed, then I would imagine that range would be determined by weapon size. Therefore, plasma weaponry in space would have a unique property shared with lasers, but not kinetics: you trade range for damage at any given weapon.

Capital ship weapons, being the largest, would therefore travel the fastest and do the most damage (likewise implying they could do the damage of a smaller weapon at a longer range).

I still wonder, though. If you're firing what's essentially superheated blobs of gas at relativistic velocities, would most of the damage just be kinetic? I don't have any maths, but...gut...tells me that the impact of the matter itself would swamp out any damage caused by the superheating.

VonMalcolm:Eek! That's a lot of work just to get underline text. I think I'm starting to see why programs such as Dreamweaver are so popular nowadays.

Thanks though.

Citizen Joe:Treating plasma bolt matter as a supercharged liquid instead of a gas? Interesting idea, since it does solve my little density question in addition of giving me more reason to utilize cartirage-based rounds for plasma munition feed akin to this article on weaponized plasma. Now that I think of it, I'm now wondering if its even possible to freeze Anti-Hydrogen into a liquid state for storage and/or call it "Fluid Anti-Hydrogen".

ElAntonius:To be honest, I wasn't really sure if Plasma Bolts would cause any additional damage effects beyond that of thermal. Some Kinetic Energy transfer and Electrical (since I imagine the bolt to be highly charged once it leaves the weapon system proper) discharges, but from what you're suggesting, such damage would potentially be overshadowed by the pure thermal damage potential.

As for the scale of the vehicle/craft that the weapon is mounted, well it could only be logical that a capital starcraft would have enough energy to shot the DEW round farter and faster than any Small Arm equivilant could, never mind the higher damage potential. Though, to be honest, I never really thought about the idea of adjusting the power flow of a bolt to deliver either more range or more damage. Even the idea of adjusting lasers for such a setting past my mind.

I imagine that with the additional mechanics and systems required to have a proper weaponized travel at combat ranges would limit the micronization to vehicular mounts and even SAW scale weapons would still require Power Armor with strong enough actuators and holding it with two hands/manipulators/whatever to properly wield the weapon.

The same would go with Particle Beams if only because I'm not really sure if there is a way to solve the "radiation on shooter" problem outside of mounting the weapon in front of some metal and/or mass that protects the onboard crew.

OK, let me see...plasma isn't steam; while you can create plasma by heating something and 'boiling off' electrons; you can also produce plasma by using ionizing radiation or powerful voltages. plasma is nothing more or less than a bunch of positive ions imbedded in a cloud of electrons that, while independent of individual atoms, cannot excape the combined attraction of the mass of the poisitive ions. While electrically neutral, plasma is highly charged and so subject to electric and magnetic fields...you can 'imprint' a magnetic field on highly charged, well, anything, plasma included. This 'imprinted' field is both reversed and weaker than the original...and it fades more or less quickly, depending on the streingth of the original field, the energy level of the ionization, the tempurature of the material, its density, the chemical make-up, and how long it was subjected to the original magnetic field. Finally, the effective range of a non-solid bolt is velocity vs expansion; determining the threshold for effective density, I'd guess (purely off the top of my head (english is such a weird language):), that after it drops below 1 gram per cubic centimeter, it will do very little damage at even triple digit per second velocities. In an atmosphere, a plasma bolt would act much the same as an explosive shaped charge; in space, the bolt would fly straight...until local magnetic, charged-particle-streams, or electric field/currents made it curve...although it probably would dissapate long before that. Of course, using a nuclear shaped charge to throw a jet of incandescent metal steam at triple or qudrupal digit velocities and at tempuratures of hundreds of thousands or even millions of degrees...think of an anti-tank weapon only magnified by tens of millions in terms of power.

ElAntonius:"Picking some random numbers (Ignore them as you will, I put them in for context):

What are the effects of a 1g/cm blob of plasma striking a 1m radius at .9c?"

KABOOM!!!! :)

On another note; maybe the easyist solution to "go anywhere FTL" use a 'spherical error' at the target star system; i.e., when you drop out of warp you know that it well be somewhere within x number of miles/kilometers of your target point. Example; starship XYZ drops out of warp in the Banana System; he was aiming for the local L4 point...but winds up 80,000 kilometers sunward and 1400 KM 'north' of L4...well within the 100,000 KM spherical error...

After re-reading the stardestroyer.net article, it noted that (barring any magi-tech to keep cohesion of the plasmoid beyond the magnetic field of the weapon system) the bolt will disperse in about a thousanth of a second.

From that lifespan suggestion, I calcuated that the Maximum Effective Range of the plasma bolt ranges from 2997.9meters for a plasma bolt moving at 1% the velocity of light to 149,896.2 meters at 50% the velocity of light. Why no higher? Something tells me that it takes a considerable amount of energy to accelerate said plasmoid bolt to move at relavistic velocities and half the velocity of light just might be the limit. These ranges are acceptible to me since, comparably, plasma bolts are incredibly close range compared to other forms of conventional munitions such as machineguns, chainguns and most types of missiles.

Density-wise, well from the comments I've read, I envision the plasmoid to be "fluid" density: denser then gas (such as an atmosphere) yet not as dense as liquid like water. I'm unsure of the volume of the bolt itself, but in my setting the bolt originates from a cartirage aproximately the same mass and/or volume as a .50 cal round. It may not even be the entire mass is converted into the plasmoid in that at least half that volume is spent powering the mechanisms to produce and launch the bolt. I'm unsure as to what the energy yield and the minimum output the bolt would possess, but something tells me that the previous descriptions would amount to what is refered to as "cold" plasma which would probably still be measured in thousands of kelvins. Potentially enough to super heat and weaken, if not melt, structural steel.

From those descriptions, what would be the "charge" of that bolt, minimum power output and magnetic field strength required to produce said bolt, and additional damage effect said bolt would perform to a target beyond thermal. With plasma, it's pretty much a given.

As for the "kaboom" comment, well not to be a party pooper but a kaboom (not neccessarily Earth Shattering, but not neccessarily out of the question) is to be expected of anything traveling that close to the velocity of light. Only possible exemptions would be photons, electromagnetic waves, and space-time and that's probably a good thing.

First, a definition: a plasmoid is a coherent structure of plasma and magnetic fields, such as a plasma "ball" or "bolt".

There is a theorem, called the Virial Theoremhttp://en.wikipedia.org/wiki/Virial_theorem#Inclusion_of_electromagnetic_fieldswhich proves, quite generally, that any plasmoid will expand continually unless constrained by external forces, no matter what internal structure it has. If you want to shoot a plasmoid at someone, you need to get it to him before it expands into harmlessness. A relatively cold plasma will expand at somewhere in the vicinity of 60 km/s (the speed of the ion-acoustic wave of ionized hydrogen at a temperature of about 10 eV). Hotter plasmas expand faster. Plasmas with internal currents and magnetic fields will expand faster.

In an atmosphere, a plasmoid can be confined by the pressure of the surrounding air. If a plasmoid has a volume V and a pressure P (equal to the pressure of the surrounding atmosphere, so it does not blow itself apart), it will have an energy somewhere between 1.5 P V (for reasonable temperatures) and P V (for temperatures so high that the thermal velocity of the ions are relativistic, or for strong internal currents and magnetic fields). In SI units, the atmosphere has a pressure of 100,000 Pa, and volume is measured in cubic meters. It takes about 1,000,000 J to cause incapacitating surface burns, and perhaps 100,000 J to produce an explosion that causes incapacitating trauma. Thus we can see that a plasma bolt for use in an atmosphere will have a volume of somewhere around 1 m^3 to 10 m^3 - probably more, since this assumes full transfer of energy to the target. The plasma will be hot (there are cold plasmas, but heat energy flows from hot to cold so we don't want these since they will not deliver thermal energy to the target). Hot plasma means for a given volume and pressure (hence for a given energy) there will be less "stuff" in it. This means the plasma "bolt" will have a density significantly less than that of the surrounding air. Low density fluids have very little penetration through denser fluids - they tend to immediately slow down and disperse. It is looking like plasmas will not be much use as weapons in air. Because of their rate of expansion, they will not be much use in vacuum, either.

All this assumes we want to use the thermal energy of the plasma to cause damage. As I described earlier, particle beams which have relativistic protons accompanied by enough electrons to neutralize their charge will be beams of relativistic plasmas. When they strike a target, the protons will smash into the target's atoms, flinging them all over while jolting the nearby electrons to ultra-high temperatures. This will heat the target. Meanwhile, the protons will have enough penetration to punch through many tens of centimeters, perhaps a meter or so, of condensed matter (water, iron, lead, diamondoid - any kind of solid or liquid). If the protons are very relativistic, the individual protons will not go much more than a meter through condensed matter, but they will smash the nuclei of atoms they hit into fragments that will penetrate even further (and these secondary projectiles may, themselves, smash more nuclei into fragments), creating a deeply penetrating shower of radiation. This form of plasma weapon will cause damage by heating the target and/or delivering radiation dose. It could have a reasonable range in vacuum, and may end up being a useful space weapon.

A couple of misconceptions I noted:(1) Plasmas are gases that behave oddly around magnetic fields. They do not behave like liquids. If you do not have magnetic fields around, a plasma behaves just like a hit gas.(2) Plasmas are not strongly attracted toward electrically charged objects unless the plasma, itself, has an electric charge. Giving an electric charge to a plasma just makes the plasma explode even faster.

If you can only swap bubbles of spacetime that contain the same rest mass, you solve a lot of consistency problems since the conservation laws of energy, momentum, and angular momentum are automatically satisfied. This would mean that a spacecraft can only "bubbleswap" into a mass repository - maybe an asteroid or some such.

If you move away from bubbleswap as an interstellar travel and back to interplanetary, then you could have two (or more) bubbleswap 'pods'. Then you just sync up the two masses and press the button. It might work on quantum entanglement or something. That allows for easy exchanges of crews.

On the other side of the coin, you could put one pod stationary and the other on a ship. Since unbalanced rest mass swaps result in differential momentum changes, it could be used as a thruster. But more like a balloon using ballast to get into different currents than an actual guided thruster.

Luke:Somehow, I can't help but think that giving a plasma bolt less density than air not as efficient in keeping the bolt solid along its path as is. It would be akin to shooting a bullet with the muzzle against a steel wall: It would dent it, but it wouldn't allow it to travel far. It would probably make sense if either the bolt was denser than air and ram its way through the medium or a kind of vacuum within the air is generated that could be used to channel the bolt through the air like an extended barrel.

I think we're going about the plasma weapons the wrong way. What we are looking for is a hand held device, that makes a neat sound and then lofts a glowy thingy at the target slow enough that you can see it travel which then does damage on impact. To me, that says chemical paint balls.

That's the basic problem. You want a plasma bolt to be denser than air, for penetration. You also want it to be hotter than air, for energy transfer to the target. Denser and hotter than air means a higher pressure than air, so that the plasma bolt blows itself apart at 60 km/s or more.

All the methods I've been able to think of for creating a semi-evacuated channel through air would be more effectively employed by using them directly on the target rather than the air between you and the target. Remember, the pressure of the air times the volume of air in the beam path (times 3/2) is the energy you have to supply to evacuate the channel, and then you need to continue to supply energy to keep the air from rushing back in at 330 m/s.

Actually, we already have 'plasma' weapons...they use a chemical explosive to heat, compress, and propel a hunk or metal; changing it from a cone into a supersonic jet...it has been used since WWII as an anti-tank weapon. I don't see it as a cool Sci Fi weapon, though.

Perhaps the bubbleswap could be used planet to planet, or just star to star, from orbits that have compatable relitive velocities...

Here's another weapon concept...fire elctrostaticly charged , spinning, disks of dust (the two forces balance), and launch them at at least 1% of light-speed; these 'dust' torpedoes would be low mass, but have a huge impact; if you fired several disks, one right after the other, made out of radioactive material, then the impact would cause a nuclear explosion: my question is 'would I actually need that high of an impact or could I trigger the nuclear explosion at a lower velocity?'

Charged spinning disks will have two "forces" trying to blow them apart - the electrostatic repulsion and the centrifugal force of rotation. You can't make them balance in order to maintain cohesiveness. If you can launch them at 1% light speed, you could launch a stream of uncharged, non-spinning dust at 1% light speed. An impact with such a near-relativistic dust stream could cause significant damage.

I'm pretty sure that any relativistic weapon is not going to be man portable.

While not currently weapons, there are certainly man portable devices that can project relativistic bits. In particular, anything that can generate on the order of 500 kV of potential or more will accelerate electrons to relativistic speeds. It is not difficult to imagine a man-portable electron beam weapon, which would project highly relativistic beams.

What makes a weapon effective is the terminal effects of whatever you are shooting.

A 500 kV electron gun will be severely limited by the amount of current it can send. Old TVs have high energy electron guns, but the amperage was low enough that the living room wasn't flooded with lethal radiation. A weapons grade electron gun needs a high amperage power supply, heavy duty cableing and an efficient cooling system in order to work, much more mass to carry with you (and then add the laser needed to carve the channel through the air for the beam to follow!).

While we are all fans of spectacular terminal effects from years of movies (I am waiting for a gigaton nuclear or kinetic ground burst), it may be that future devices will become far more subtle. EMP devices to confuse enemy and carbon fiber dust to disrupt electric grids have already been demonstrated, "smart bombs" are far smaller than the ones they replace and computerized sights promise to make every soldier a marksman.

From the general consensus, it seems that free-floating "bolts" of plasma as projectiles isn't exaclty what one would call "hard SF". Still, the requirement of an electromagnetic barrel to augment the physical one attached to the Plasma Bolter does solve my criteria of plasma bolts in my setting having a very short effective range yet still have high damage potential. Though something tells me that it'll be very difficult technologically to fit the entire plasma bolter weapon into a scale that could be easily wielded by power armored troups and would make more sense as a vehicular-mounted weapon.

However, I really haven't had an answer to my IP Drive augment system in one of my earlier posts (at least, I don't think so....). The one that is essentially Star Trek's Warp Drive but requires a rocket engine to get moving and makes for a horribly poor interstellar drive (or at least the human varient).

The Warp Drive in my setting allows for the design and use of spacecraft to have an average 50% boost in its DeltaV budget than a similar, unequipted spacecraft. However I am unsure if this is achieved by higher acceleration/velocity, a remass tank that is significantly smaller than what would be normally, or a hybrid combination of the above two?

And another idea that recently popped into my head the other night as I was reading materiel from an RPG book. To be more blunt, it's what I'd like to call a hybrid STL colony craft whose onboard payload is mainly genetic material preserved in suspended animation not unlike a Seeder Ship, yet it has an onboard crew that mantains and manages the onboard craft systems to ensure that everything works properly. This crew are required to have work shifts of a year per each fifty years in suspended animation which is similar to the classic SF cliche of the sleeper, longer if said crew raise children to maturity but limited to one surving child at a time to ensure genetic divercity not unlike a generation ship.

So, is this style of STL Colony ship possible or is it just a bad idea waiting to happen?

A normal body has its own regenerative properties. A body in stasis (cryosleep) does not. All bodies in space suffer from radiation damage. In order to prevent waking up dead, you need to spend time out of cryo to heal any radiation damage.

That could also mean that most of the time out of stasis is spent in a sick bed trying to heal yourself.

Your IP transfer drive can function on this principle: Power up your warp field coil, collapse the space in front of you, thrust through the collapsed space, release warp field behind you. You are now 1 warp field bubble diameter farther away than you started. The problem with this is that your physical speed doesn't accelerate, you remain at some constant speed dictated by your field size and cycling rate. Traveling 1 AU/day is pretty fast, but that is still 500 years to the nearest star. When you do the leap from star to star, you're basically collapsing a narrow column between two stars all at once, thus one hop. The military can probably do the same IP hop in-system. The civilian grade hops are much shorter though, thus not suitable for interstellar transit. Restrictions for the IP-C drive probably include empty space in the field being collapsed. Which means that once you get close to a planet, you have to rely on regular thrusters. This also guarantees that you don't run into anything in the collapsed space, since it won't collapse unless it is empty.

Citizen Joe:- Suspended Animation:I have taken that little raidation damage into account when my little thought proposal came into my mind when I recalled Atomic Rocket's little entry on the Sleeper Ship. Though, to be honest, I have no idea how long it takes for an adult body to heal from said radiation damage after such a long period of sleep. But then again, perhaps the "Year of labor per sleep cycle" doesn't call into acount the time spent recovering from hypersleep? Perhaps even helping those recovering from stasus can be included as part of the shift requirement as well?

- IP Warp Drive:Somehow, your idea of an IP Warp Drive's operating principle reminds me of a nuclear pulse drive. Even so, it does match my criteria of an IP Warp Drive that makes for a lowsy Star Drive timewise, though I had imagined it to be a thousand years in respect to the onboard crew rather then a thousand. Perhaps 0.5 AU per day might work out?

I also imagined that even with the IP Warp Drive, the path of a spacecraft will still follow a Brachistochrone Orbit or similar since it's not completely isolated from the sun's gravity. However, I'm figuring that the gravity fields of other celestial bodies would decrease an otherwise efficient form of interplanetary transport. Twenty times the celestial body's radius should be a good minimum distance, since ten radii sounds a bit close and fourty is just overkill.

However, you did state that the fluctuating warp field doesn't allow for accelerations of any kind, but rather a fixed velocity. It suggests to me that having torch crafts accelerating at about 1 G to stimulate Earth gravity is an impossibility. Perhaps there's another way to marry the two together?

As an example, lets assume that your warp drive can compress 1km/s and has a range of 1km. The power requirements for keeping the space compressed is directly related to the volume of space compressed. So we'll say you've got a power limit to 50 km of space compressible. In order to get the maximum compression, it would take you 50 seconds to cross the 1 km range of your warp drive, at which point you cross the boundary and you have traveled 50km (warped) + 1km normal. Your physical speed would be 1/50 km/s while your apparent speed would be about 1 km/s.

Now that isn't terribly impressive and you spend most of your time in real space rather than crossing boundaries. However, you could probably vary the numbers to get your .5 AU/day travel times. I'd recommend the jump length to be related to the hull length and the cycling rate to be in microseconds.

As to your gravity issue, you could have the side effect of the threshold jumps (traveling through warped space) cause apparent micro bursts of acceleration which simulate the gravity. This is like a florescent bulb where it only gets power like half the time but it occurs at a fast frequency so it seems like the light stays on. The gravity isn't a constant 1G, it is a rapid pulse which averages out to 1G. Once you drop out of warp, you lose gravity though. However, at that point, you're closing in on your destination and need to fire up your reaction thrusters to match speed and such.

As a side note, this sort of burst gravity would probably cause motion sickness in some people, which makes them unsuitable for IP travel in this method. Likewise plot device sensitive objects may not be able to withstand that activity either. Do not use warp travel if you have a heart condition or pregnant...

Warp Field generation and collapse cycle measured in mili-seconds that could be confused as continually on, an average acceleration of 1 G with mili-second moments of micro-gravity, sounds like a good operation mechanic for my IP Warp Drive idea. Though the motion sickness and such note kind of reminds me of those warning signs at amusment parks on rides. Then again, it does give ample reason to have non-Warp equipted Torch Crafts other then possible costs.

And speaking of numbers, I don't suppose that you have an idea as to how to calculate a particular craft's warp field maximum radii or at least where to begin? I know the variables should be superior spacecraft dimension, minimum energy output, acceleraton/velocity of spacecraft, and potentially environmental gravity force. Beyond that, and how to assemble said equation, I'm not really sure.

Same with my Hyperspace Warp Dive equation that I had some aid from Rick some time last year, but that should be saved for another time.

- Hybrid STL Colonyship

So other then that radiation healing period, there's nothing wrong with my little Hybrid Colonyship idea?

From the discussion of Lithium and Trinium as an alturnataive method of creating He3 as opposed to gas mining upon the gas giants such as Saturn and Uranus, it does put a wrench in my plans on having the gas giants of an outer solar system (that has gas giants in the first place) as a strategic battlefield akin to the Persian Gulf. Especially since I have imagined the majority of the hostile alien powers in my setting to require "empty space" that keeps them from the more habitable inner planets of a star system beyond good old fashion rocket-based travel and similar.

Beyond the Rule of Cool, how might one justify the mining of He3 upon gas giants?

And while we're on the subject, beyond fusion fuel and fission reactor water, what else is Deuterium used for?

"And speaking of numbers, I don't suppose that you have an idea as to how to calculate a particular craft's warp field maximum radii or at least where to begin? I know the variables should be superior spacecraft dimension, minimum energy output, acceleraton/velocity of spacecraft, and potentially environmental gravity force. Beyond that, and how to assemble said equation, I'm not really sure."

I'd go with either Joules or Watts per cubic meter and have the 'field' be the maximum diameter of the ship and twice the length.

"Beyond the Rule of Cool, how might one justify the mining of He3 upon gas giants?"

Either as Starship fuel, (with the refueling station being part of the mining/refining outpost); or, have the He3 be used as reactor fuel for local use (perhaps as the power source for an antimatter factory).

IP Warp: Whatever the size of the compressed space is, you'll want your ship to be longer than that. You need to prevent your own mass from touching off the expansion of the compressed space. So you'll need a protective field and the ability to be on both sides of the compressed area. You may also want it long enough that the leading edge can compress the next section of space while the rest of the ship is still passing through the compressed area(s). That might look a bit like flying through a series of rings. Visually, you probably wouldn't see anything, although the warping might create a lensing effect, which may reflect the host star, so ya colorful rings being flown through.

Li, D, T: Lithium isn't very abundant. Take a look at the chart half way down this page:http://en.wikipedia.org/wiki/Abundance_of_the_chemical_elementsThere is a major drop off after Helium. So your lithium and boron becomes pretty rare. Combine that with the 'useful' isotopes being rarer still. If you use up all your lithium and boron, then what do you do?I've found that Lithium and Boron can be formed by cosmic ray spallation of heavier elements like oxygen and nitrogen. So I like to use that nasty radiation belt around Jupiter as the basis for producing spallated lithium/boron as well as some other trace elements. Then that stuff gets fished out with ships and processed. Meanwhile, you're getting 1 part per million He3 from regular helium. And helium is a million times more abundant than lithium. So it is a bit of a wash.

He3 justification: Earth is only habitable planet. Environment is almost totally destroyed by radiation and chemicals. Humans need power so they use He3-He3 clean reactors. They can't breed He3 on Earth or risk further contamination of the ecosystem. So the breeding it done in space.

Citizen Joe:- IP Warp:Spacecraft longer than Warp Field, protective field against space-time expansion, I think I can visualize that. However the rest: Being on both sides of the space-time compression field, dual space-time compression fields, is probably something that could use a diagram of some sort. Unless I'm getting the visualization wrong, the warp field is starting to look less and less like a bubble as imagined by Miguel Alcubierre and more like some kind of dumb-bell shaped field with oval-like "weights".

- H3-3 Justifiation:Continued discussion of Lithium-Boron method of He3 production on the War of the Rings blog entry shows that though the process is easier, there are some hicups that make Gas Giant mining much more appealing. If the generation of Lithium could be made by utilizing the Jovian Radiation Belt from Oxygen and Nitrogen, then it might make the Lithium-to-Trinium process of He3 production compeditive to simple mining of Uranus and Neptune. Perhaps instead both are utilized to make He3 a more economically viable source of fuel for Deuterium-He3 Fusion reactors?

As for that Earth Habitability rationale, well I have imagined that the World War that scattered humanity across the stars to have a detrimental effect on the global environment in the form of radiation and chemical contaminated wastelands, I really didn't imagine it to be the only habitable planet in my setting, let alone one with a developed infrastructure. Perhaps it would be best described as the only habitable planet that doesn't require extensive life support systems to support a high planetary population like were we are now?

Ferrell:- D-He3 Fusion powered Anti-Matter factories: A Fusion powered Anti-Matter production facility isn't such a bad idea, though I already imagined particle-accelerator type production/replecation stations that are solar powered and orbit a star at about within Mercury Orbit. Wouldn't solar power be enough to support Anti-Matter production or would it need a helping hand from fusion?

- Deuterium for Starships: Did you mean "fuel" as in for onboard reactors or as a mistype of remass for rockets?

And now, some random questions: Since Plasma "Bolts" style weaponry aren't exactly possible without an extended electromagnetic barrel, is it possible to have Plasma "explosive" warheads that range from ICBM-Cruise Missile -esque Spacecraft busters down to shoulder launched munitions? Hand-held grenades if I do so dare? And if so, how much of an explosive yield will we be talking about?

Another is the idea of sapient macro-scale floating organisms. No, I'm not talking about giant floaters and other such Sky Whales for a gas giant, though it's not such a bad idea. I'm leaning towards terrestrial floaters such as the Eosapiens of Darwin IV. My question is if it is not too much of a leap of faith to postulate floaters becoming a star-faring civilization?

The yield depends on what sort of energy source you have packed into your warheads. Modern explosives have a specific energy of about 4 MJ/kg. If, for example, you have electrical storage devices with specific energies greater than this, you can either have your storage devices explode or (if they can discharge fast enough) discharge their stored energy in an electric arc that produces an explosion. The latter design could be called a plasma explosive, if you like, since the glowy bits of electric arcs are plasmas. So if, for example, your electric batteries store 8 MJ/kg, they would explode with twice the blast effect of an equivalent mass of high explosive.

The absolute most energy you can pack into batteries (or capacitors, flywheels, torsion springs, superconducting solenoids, or any other energy storage device) made of normal matter and without using nuclear effects is about 40 MJ/kg to 50 MJ/kg. That is the limit of what chemical bonds can handle before they break (blowing your battery to bits before you get to use it). Electromagnetic fields can't get past these limits - the fields produce stresses and pressures that will break your battery if the stored energy exceeds this limit. Note that this is the theoretical maximum - practical maximum energy storage can be a lot lower than this (and is, for modern energy storage). By some reckoning, you can get around this limit by only counting part of the mass of the reacting system - gasoline burning in oxygen stores about 15 MJ per kg of gasoline/oxygen mix, but if you don't care about the oxygen because you can get it for free without carrying it around, you can treat it as if gasoline stores 40 MJ/kg.

So decide how potent your batteries are. This tells you how powerful non-nuclear explosives can be.

Sabersonic: "- Deuterium for Starships: Did you mean "fuel" as in for onboard reactors or as a mistype of remass for rockets?"Actually, both; sorry for the confution, I think I typed that late at night when I was tired.

As for plasma weapons, yes, very short range weapons (if plasma expands at 80km/s and you have to launch it at at least that fast, or faster, then you now have a 'blaster'; especially if you shoot it in the atmosphere), but if you can use an ultracapasitor to turn a small amount of, say, Mercury into a plasma, then that 80km/s expantion would be pretty devistating.

I have been thinking about this for a while...Relitivistic velocity weapons; R-Bombs for short. I've got some questions about them:

1. How do you launch one without a quarter of the gallaxy seeing it?

2. If , as some say, you cannot determine the position of an object travelling at .9c plus,; then how would you navigate an STL starship, much less a ballistic R-Bomb? Either you can't determine your position (just as an outside observer would, or wouldn't), or you can determine your position and thus you do know where the R-Bomb is during it's flight; if you can detect it, determine it's speed and distance, use some math, then you can determine where it's at NOW, thus enabling you to intercept it.

3. Now, if you launch this thing, at say .9c, and it has a square face (1000m x1000m = 1000000m) then it will strike 270,000,000,000 cubic meters per second; if there are only 3 atoms per cubic meter, then your R-Bomb will strike 810,000,000,000 atoms per second, and they will explode on impact. So, your ballistic R-Bomb will glow and be slowed over time (years, decades, centuries...). So, no steath interstellar projectiles, and a limited effective range?

4. Wouldn't using some sort of magnetic field to keep the interstellar medium from impacting the R-Bomb also cause brakeing and need a power source that produced a lot of waste heat?

5. If you used some sort of engine to counter the brakeing effect, wouldn't you be able to see it from lightyears away?

And finally,6. wouldn't all of the above limit an R-Bomb to just interplanetary, not interstellar effective ranges?

Luke:- Plasma Explosives: The way you describe electric arc explosive makes it that it would be more appropriate to call them Plasma Arc explosives, though the idea of the yield dependent upon the internal storage capacity does give rise to the idea of variable yield warheads that could range from EMP and stun effect to Anti-Armor. And considering that the Plasma Arc doesn't mention anything about the device being destroyed after the initial discharge, perhaps that makes a Plasma Arc Grenade reusable?

Ferrell:- Deuterium for Starships: Well that answered my question, though now I'm wondering how well Deuterium is as remass?

- Plasma Bolts: Well, one would think that moving a plasma bolt through freespace at high speeds would keep it coherent enough to be a viable ranged weapon system. However, previous discussion kind of disways such thoughts since it either puffs out into nothing if its too dense or crashes into air if the atmosphere itself is denser than the plasma bolt itself once it leaves the confindes of the barrel. The best solution would be to have an extended electromagnetic barrel beyond the physical one that determines maximum effective range.

Though it does give one thought: If it can't be weaponized as a free-space bolt, what about the idea of a plasma-based flamethrower?

Ferrel:- Interstellar R-Bomb:1) Something tells me that it can only be achieved through magi-tech if only because the waste heat (let alone the energy used to accelerate said R-Bomb in the first place) would produce so much energy that it might even eclipse that of the parent star. Granted, thermal energy travels at the speed of light and would take light-years for the nearest civilization to detect it.

2) That one I never really heard before. Previously I thought that if you can detect such an object and observe it for any lenght of time, you could determine its velocity and calculate its course from its first known position.

3) If said R-Bomb can be slowed, without the relativistic effects of weapon to the stray hydrogen atom making it go "boom" prematurely, then it would probably have a limited range even if the remass and/or fuel capacity isn't an issue. Sooner or later it'll slow down and become "dead" in space (no pun intended).

4) Well if it caused drag on a Bussard Ranjet to give it a maxium velocity, then yes it would probably slow the R-bomb down. The lifespan of the onboard powerplant needed to power the "Navigation Array", assuming that the R-Bomb doesn't have one in the first place, would also give the weapon a limited range as well. The waste heat would also be an issue in that it would require radiators to be deployed while en route to the target.

5) Anything on a spacecraft that generates energy to power something is going to be seen on a thermographic sensor. After all, we're able to measure the temperature of distant stars, though now that I think of it the waste heat would be insignificantly small by comparison. Though then again just because you can detect an object moving at relatevistic velocities doesn't exactly guarantee that one would have enough time to do something about it.

6) If the variables were enough to reduce the effective range of an R-Bomb from "infinite" to a measurable range and that range is exponentially less than a galaxy, then for the purposes of preemptive strike in a war that must be decided here and now the R-Bomb would be best deployed at interplanetary ranges. If one is willing to wait millenia to have the weapon reach its designated target(s) then its a near-ideal fire-and-forget weapon. Only problem is that the world/star system you're protecting might be attacked by an enemy's own R-Bomb or invasion force by the time your own R-Bomb reached its target.

And now for another random question: Is it physically possible to have lasers operate as effective weapons in water?

Well, you're going to need some way to generate the plasma in order to make it explode - an electric arc is one fairly direct method if you have electric energy available.

In order to re-use an arc grenade of the sort described, it will need to be able to survive direct contact with an explosion more intense than that generated by modern high explosives. Even though the grenade would be made of tough stuff, I imagine it would get pretty beat up, and maybe completely disintegrated, by the blast.

Plasma flame-throwers have many of the limitations of plasma bolt guns. If the jet of plasma is at greater than atmospheric pressure, it will very rapidly expand until it is at atmospheric pressure. Thus, at any reasonable range the jet will be at ambient pressure. To get ambient pressure, you can have a cold, dense jet or a hot, low density jet. A cold jet rather defeats the purpose of a flame-thrower, since it is not going to burn anything. A hot jet will have low density and will have trouble punching through a reasonable distance of air. There is also the issue of coupling the plasma energy to the target - the target will only be in thermal contact with a thin layer of the plasma, which insulates the target from the rest of the plasma, resulting in most of the plasma just going around or bouncing off the target without heating the target.

Now you can get hot, ambient pressure plasmas to propagate for short distances through air, and to dump their energy well enough to cut metal. I don't see how you can get it to go more than a few nozzle diameters, though.

If, for some reason, deuterium is very cheap, you can use it for propellant. For some fusion rockets, you have no choice but to use deuterium as propellant, since you are leaking the fusing plasma out into space while only burning a small fraction of it. In this latter case, deuterium is both propellant and fuel (and probably also either tritium or helium-3, as well).

Lasers emitting beams that are in the green, blue, or near ultraviolet parts of the spectrum can penetrate tens of meters through clean water without significant attenuation. The more junk there is in the water, the more attenuation of the beam.

2. There is no reason you can't determine the position of high relativistic objects. Some arguments for using relativistic projectiles in interstellar warfare give that since the projectile is going almost as fast as its light, once you see the object, it is almost upon you and you don't have much time to prepare. However, given point 1, above, the launch process will probably give plenty of warning time.

3. Using your figures (3 hydrogen atoms per cubic meter at 0.9 c) you will absorb about 0.16 watts per square meter. This will reach a steady state where heat coming in (from impacting hydrogen plus heat from the cosmic microwave background) equals heat going out (from thermal radiation) at a temperature of 41 K. 41 K is pretty cold, cold enough that nitrogen is still a solid, for example. At 41 K, it will not be very visible.

At 3 hydrogen atoms per cubic meter at 0.9 c, the relativistic projectile will experience a drag pressure of about 1E-18 N/m^2. Over a full year, this corresponds to a change in momentum of about 3E-11 kg m/s per square meter of frontal area. If the projectile is a 1 meter by 1 meter by 1 meter block of iron (1 m^2 frontal area, 7.8E3 kg), it would not have slowed down appreciably over the entire lifetime of the observable universe (assuming constant physical conditions, that is - I'm neglecting that the early universe was much denser than it is now).

4. A magnetic "deflector" field would cause some drag. The field will not necessarily use any energy - a ferromagnet or superconductor can maintain a field without dissipating any energy.

5. Not using the parameters of point 3, above.

6. What limits the R-bomb is that your target will likely see the launch, and then put something in the way a good distance from the planet they are trying to protect. At 0.9 c, a 1 gram bit of gravel will explode against the projectile with about 30 kilotons of explosive boom.

Luke: Ok, I had thought that there was something wrong behind the R-Bomb concept, but didn't know exactly what...thanks for clearing that up. Although, it occures to me that any civilization that could acuratly target a planet at interstellar distances could just zap that world with a laser or artificial GRB...also, wouldn't the Oort Cloud be a major obstical to any R-Bomb?

Luke:- Plasma Arc Grenade:Well I do have two ideas on plasma arc generation. One is to have wire(s) with anchors on the end deployed from the central unit and electircity flows through it. The other is to have an open circuit and a gas injector to generate a conducting cloud. Granted, I have no idea how plausible either are in generating the plasma arc based explosion. I am open to other ideas though.

And speaking of explosions, such a grenade rugged enough to survive an explosion with a yield twice the equivilent conventional explosive mass would probably make it either expensive or heavy for normal grunt work. Oh well, it was worth a shot.

Though now I'm wondering if there's a way to have a grenade that's a credible threat to power armor outside of shoulder mounted rockets and shape charged rifle grenades.

- Deuterium Fuel and Remass:As far as I know, Deuterium is harvested from water. Granted, water is plentiful in the form of ice and hydrogen gas in gas planets (how much ppm on each gas giant, no idea), it doesn't really equate to economical Deuterium as in propellant fuel in addition to fusion reactor fuel.

Though then again, it does give even more plausability and reason to keep my solar powered particle accelerators orbiting close to the sun. Not only in the production/replecation of Anti-Hydrogen, but for Deuterium as well.

Ferrel:- R-Bomb and Oort Cloud:Somehow I doubt that the density of the Oort Cloud of any starsystem is significant enough to be an obstacle. If I remember correctly, the Asteroid Belt has an average distance between asteroides of about sixteen times the distance between the Earth and the Moon and it's pretty much the densest collection of junk in the solar system outside planetary rings.

While it is unlikely to hit something in an oort cloud, you don't want to wait a thousand years and then oops! hit a grain of sand. That means you have to plan for that contingency. Just like the target can't really see your R-bomb, your R-bomb can't really see stuff in front of it.

Since we're still on the subject of weapon systems, lets see if anyone can answer these questions.

I don't really remember which blog entry featured this comment, but one commentor stated that the Sensor Operator and Weapons Gunner should occupy the same seat since if a Sensor Op could detect a threat then it would be more effiicent to just have them have the fire button ready to be pressed and take it out rather then to just report the detection of such object (assuming that the "weapons free" order is issued). My setting has spacecraft that utilize Lidar and Ladar sensors for detection, navigation and targeting and I'm wondering if it isn't that big a leap to postulate that Ladars could be utilized as low powered laser point defense systems?

The Main Gun of tanks are smooth bore to allow more versatile rounds to tackle a variety of threats with the more well known being Kinetic Penetrators used against other MBTs and HEAT rounds for more "light skinned" targets. So would it be possible in a near-far future setting for armored fighting vehicles equipted with Particle Beam weaponry to have the same variable yield as contemporary main guns or would this make more sense with Electromagnetic Guns?

And speaking of Particle Beams, how does one solve the little radiation problem for the shooter when said DEW types are fired?

I see no reason why a multi-purpose laser couldn't serve the dual purpose of lidar and blasting things. You might want two separate beam pointers for the laser - one is a small scope that can rapidly spin to point at new positions - this is a wide field lidar scanner. The second is a large scope that can be used for narrow focus, high resolution lidar and also zapping things.

I could see variable yield particle beams. Just emit more electron bunches in a burst, for more energy and more ability to bore through both armor and air. I could also see variable energy projectiles from electromagnetic guns.

The usual method of protecting the operator from radiation backscatter of particle beams is to have him behind a shield - depending on the type of particle beam, a few centimeters of lead, several centimeters of borated polyethylene, and maybe several centimeters of iron.

- Lidar/LADAR Blaster:I'll take that as a "yes" then to the previous question. Granted, the larger scope will have to be placed stragegically across the spacecraft as to reduce the amount of blind spots and increase zones of crossfire.

- Particle and Electromagnetic Tank Guns:So another "yes" in that question as well. The EM Gun would no doubt have variable yield and warheads, though I wasn't really sure about the charged particle beam.

It does allow one to postulate two-man MBTs if one doesn't have to worry about a loader. Though then again if something were to hit the main power supply....

- Particle Beam Protection:

I think it's safe to assume that particle beam weaponry would be best mounted upon environmentally sealed and radiation protected vehicles and spacecraft. I figured as much but I thought that there was some way to reduce or eliminate the radiation backwash of firing a charged particle weapon.

And spekaing of spacecraft, a scientifically accurate rocketship is designed with its decks stacked like a sky scraper rather then as a surface ship to which gravity is simulated by the acceleration of the torch drive. However the trip does require a deacceleration phase to which the rocket engine is flipped towards the destination or else risk overshooting into empty space and certain doom. What I want to know is if it is possible to arrange the interior so that the transition of floors and cieling is not so dramatic as to warrant two sinks?

Let me reword my question: After the flip of the rocket ship and it enters the deceleration phase of the interplanetary journey, how does one design the decks when the ceiling during the acceleration phase becomes the floor during the deceleration phase of the trip and vise versa without having to include such drastic additions such as double of everything?

You don't. When you flip, you accelerate in the opposite direction. 'Down' is always in the direction of the thrust. Don't think of it as acceleration and deceleration phases, think of it as acceleration towards and away from the destination.

Citizen Joe:Beyond the technical wording of the whole process, it still leaves the question of internal deck orientation during those phases. The direction of 'down' will inevitably change during the corse of the journey, though continual thrust during the flip phase described earlier would probably make the transition more smooth. Mounting individual rooms on rotating gimbals would prove to be a solution, but one that has maintenance and mechanical problems of its own and something tells me that a simpler design solution is available. What that might be, I have no idea.

Sabersonic: "Citizen Joe:Beyond the technical wording of the whole process, it still leaves the question of internal deck orientation during those phases. The direction of 'down' will inevitably change during the corse of the journey, though continual thrust during the flip phase described earlier would probably make the transition more smooth. Mounting individual rooms on rotating gimbals would prove to be a solution, but one that has maintenance and mechanical problems of its own and something tells me that a simpler design solution is available. What that might be, I have no idea."

Don't worry about any of that; the passengers of your rocketship won't notice any change in the direction of "down" unless you don't have thrust during your 'flip' or end-over-end manuver at midpoint in your journey; if you do have thrust during your midpoint manuver, then they won't even notice; I susspect that what has you confused is that on Earth you have an external gravity field; however, in space, the only 'gravity' you feel is produced by the rocket engines thrusting; so long as your rocket is thrusting, the passagers will feel 'gravity' and to them, down will always be toward the engines!

Heinlein torchships performed what he always called a 'skew-flip' maneuver to go from accelerating to decelerating (which as Citizen Joe noted is just accelerating in the other direction).

This maneuver would be felt on board as if the decks were slightly tilted, but if done slowly and smoothly no one would notice.

But note that the argument for crosswise decks really only applies if your drive has high acceleration. A Realistic [TM] midfuture deep space drive with milligee acceleration does not require it, and the ship might well spin during acceleration/deceleration.

So basicly the sensation of gravity will be felt by the onboard crew and passengers in the direction of thrust no matter the orientation of the craft so long as the rocket drives are on. Somehow that seems rather backwards in my honest oppinion, but then again I'm no rocket scientist. Just trying to add in some realism to my Space Opera setting without desrupting my previously mentioned commandments for the native Milky Way civilizations.

Either way, this blog entry comments, among others, have helped me get a better grasp of the Realistic [TM] tech to make some of my ideas plausible. Other then some sapient life form designs, I really don't have much other questions for my setting. Well, unless someone has an idea on how to create a "laser trap" for a Rifle Grenade. I doubt that there's a non-magitech answer, but it wouldn't hurt to ask.

And speaking of which, I recall a commentor in a previous blog entry whose subject escapes me at the moment about having the interplanetary tanker transporting gas giant resources such as He3 with an onboard refinery to process said He3 on the way to the inner planets. Such a spacecraft may not even need an onboard crew if the automation is sophisticated and reliable enough. Though something tells me that though possible, it would be more economical to just have pure tankers to just hold and shuttle the gas but that's for another time.

My question, which is more like a brain fart now that I think about it, is what's to prevent opportunistic "pirates" from plotting an intercept course with the possibly unmaned craft and potentially equally unarmed vessel to syphon some of the He3 and/or the remass and fuel for their own use or sell it on the black market?

That was me. It was ships from the Uranus moons of Oberron and Titania. Water and or methane ice was pre filtered to increase the deuterium content. Then it got packed onto these huge tanker/refinery ships. They would crack the hydrogen out and use the waste product as 'free' remass. The hydrogen would then get vacuum distilled (which required the spin grav) in order to get the deuterium. The Deuterium was then fused to produce He3 (the real prize) and Tritium. Some of the Deuterium and Tritium was used to power fusion rockets, but most of the trip is powered by the D-D breeder reactor and VASIMIR style rockets.

A lot of the process is automated, but there's a lot of repairs, inspections, and judgment calls. The AI's aboard usually present many options but someone still has to push the button.

Anyway, what prevents pirates from jumping such a ship is the ridiculous amount of remass needed to catch up to, match speed, then depart. Of course, in a torch drive setting, that isn't really a problem. The other issue is that the He3 doesn't exist until it gets fused from deuterium. Which means there's nothing to steal for the first year or so into the trip.

Citizen Joe:"what prevents pirates from jumping such a ship is the ridiculous amount of remass needed to catch up to, match speed, then depart. Of course, in a torch drive setting, that isn't really a problem."

Well, considering that much of the spacecraft and starcraft in my setting utilize Torch Drives with a maxium acceleration of 1 G, it would probably limit potential raiders to those wealthy enough (or have enough connections to aquire) a Torch Craft. Not exactly the kind of image a "pirate" would have in such an environment, and would probably be more akin to a syndicate or mafia. Which reminds me

"The other issue is that the He3 doesn't exist until it gets fused from deuterium. Which means there's nothing to steal for the first year or so into the trip."

Which also limits potential pirate gangs to those who are able to access such information and data in addition to timing the rondevous just right to organizations who hold many a corrupt officials in their payrole. And the possiblity of these movable refineries being manned also means that the boarding parties would have to be armed enough to pacify said crew, though not enough to kill them outright. Threatening and kidnapping the crew for randsom is one thing, but such murder will only bring about unwanted attention from certain powers that have enough firepower to blow the raider craft to atoms.

It's an interesting idea, but probably something I won't really dwelve into much detail.

Though I do have one more question. In my setting, before the dark ages that caused the aformentioned five century long technological stagnation there were various interplanetary colonization projects which utilized a manner of STL propulsion system that began in the mid-to-late twenty first century and the last STL Colonization craft was deployed at about 2270. In standard sci-fi fare, these STL craft are treated with the classic "jumping the gun" gag, especially when there's an established FTL drive system. However, in my setting, due to the little dark age these colonization craft actually arrived at an extrasolar planet suitable for colonization BEFORE the FTL exploration craft. This arrival time difference varies depending upon the settlement of the colonization craft itself, with few centuries old colony worlds with the majority had "just arrived" that ranged from a whole year to a little over a month in Earth Time.

My question is, with the plausible STL Interstellar propulsion that is available for such projects in the time frame and the head start lasting for centuries, what would be the maximum radius of STL Craft settled colony worlds from Earth?

I think that the plausible STL drive will have time dilation effect on the passengers. While hundreds of years may have passed for the outside world, they may have only experienced like 50 years... much of that may have been in cold sleep.

It is conceivable that modifications to the human body need to be made to accept FTL travel. While those that grew up with those modifications may think them common place, they would be completely alien to someone 500 years older. So the irony is that the later generations may appear as deadly invading aliens to the people that have made colonies.

Well obviously there'll be noticable time dilation difference between the onboard crew and the universe outside, though this'll be more conciously apparent once one approaches relatavistic velocities. However, it still doesn't measure the settlement radii from Earth. Granted, it does give a plausible explanation as to why modern day languages such as English and Russian exist as they are despite the near millenia of linquistic evolution throughout the rest of human settled space.

However, the only Relativistic Veolcity STL engines that come to mind is the Valkyrie Antimatter Rocket Engine and the Bussard Ramjet. The Bussard has limitations of its own which includes the aformentioned drag and the Valkyrie design requires a well established Anti-Matter production industry beforehand. Either Relatavistic STL drives are highly improbable to exist between the mid-to-late twenty first century to 2270 timespan. Unless there are some details and STL designs that I have neglected to mention?

As for that note on genetic engineering to better cope with FTL travel, while an interesting idea which gives an interesting plausibility and justification for Rubber Forehead Aliens in addition to adaptation to an alien environment to call home, it has been warned that any modification to one's DNA will have unforseeable consequences that would do more harm than any theoredical good. Same with any cybernetic and bionic augmentation.

And from the lack of response to my inquiries, I'll take it that they don't have a deffinative answer, but rather vague and opinion based. If that's the case, then I guess I could take a leaf off of the ISV Venture Star and simply have the maximum acceleration of the craft be only 70% that of c. I could go as high as 90% and have it fueled by pure bull *bleep*, but something tells me that such STL Delta-V velocities aren't technically possible within the technological timeframe that I have envisioned. Granted, Atomic Rocket's Engine List has some details on various rocket engine designs and their performances, however I know absolutely nothing as to how to convert Newtons into acceleration in Earth Gravities, let alone c.

Though during the meanwhile, other thoughts have plagued my mind that would need to be addressed. One is the Magnetic Sail. It was mentioned that it could be utilized as a remass-less braking function for STL DeltaV interstellar craft. Not such a bad idea since a good portion of any interstellar journey via STL Delta-V drives would be the thrust-towards-destination phase, a.k.a. deacceleration, to enter an extrasolar system rather then fly past it. Though it does beg the question of this being an advisable system for star system entering with STL craft or if it needs to be augmented with rocket engines similar to my IP Warp Drive idea?

Another would be the Bussard Ramjet idea. Specifically the replacement of an electromagnetic ion scoup with an Electrostatic scoup. Would this design modification make the Bussard Ramjet a viable STL Interstellar Rocket alturnative or is that not possible within the 2050s-2270s timeframe I mentioned?

And speaking of IS (interstellar) STL drives, a strange thought occured just today. We all know that Anti-Matter Rockets require first the production of Anti-Matter. But after recalling the information about the aformentioned ISV, I wonder if there was a way and/or design that colonists could produce their own Anti-Matter using hydrogen from the local gas giants? Particularly using the starcraft's rocket drive and/or onboard reactor to convert Hydrogen into Anti-Hydrogen or does the process still require a city sized particle accelerator that isn't easily built into said colony starcraft?

And finally, a question that I had forgotten to ask in my previous post. In comparision, would holographic simulated environments akin to Star Trek's Holodecks be technologically possible within the next few centuries or would cyberpunk-ish VR suits be the better choice?

I ask mostly in the on-craft training of military personnel and in any area where space for training is highly limited. The simulation of walking via Virtual Reality could be utilized by a design similar to the Virtual Sphere, though other forms of movement such as running, jumping, and crawling would present more of a challenge.